# bLu vs. tLu: IS confirms 65% conversion factor



## js (Feb 6, 2006)

The time has come . . .

The time has come to talk of many things --but not in this case of cabbages and Kings and sealing wax and why the sea is boiling hot and so on,

but rather the time has come to talk of the CPF established 65 percent rule of thumb for converting bulb lumens from published specs and re-rating formulas, into torch lumens, or in other words, into lumens out the front of the light.

And the time has come for those of us who have used and defended the 65 percent figure all along to say a very loud and obnoxious "nya nya na nya na! I told you so!"

OK. Just kidding about that last part. But seriously, it does feel pretty good to find out that your back of the envelope calculations and amateur estimations turned out to be correct after all.

Now, I was one of the people who inherited the 65 percent figure. I did not derive it myself, but rather was given it by Ginseng, who suggested that it was more or less the best we could hope for and was in his experience as accurate as possible given our limited measurement capabilities. I am told that PaulW was the first person to come up with this rule, and also that NewBie/Jarhead did some calculations and basically said "Yup. That's about right."

But however that may be, I came to uphold and believe in the 65 percent transmission efficiency figure for lamps in reflectors in flashlights. It seems crazy at first glance that so much light would get lost, but there it is. It does. And after a lot of experience with incan modding and comparing lights and outputs, I no longer doubted it, but rather spent too much time and effort going around CPF trying to get people to start comparing apples to apples instead of to oranges.

Because, you might ask, "why use torch lumens at all? Why don't we all just talk bulb lumens?" and the reason is that SureFire lights are all quoted in terms of torch lumens, and the SF M6 seems to be the Lion whose tail is always being pulled. People just LOVE to talk about their 1,234 lumen Mag85's, and feel very cool when thinking that an M6 is only 500 lumens.

Now, I've given up my official position as CPF lumens ogre. I no longer care if people want to quote their bulb lumens and yet compare them to the torch lumens of other lights. More power to them! Those who know, know. And those who don't probably don't care anyway. And the whole thing just wastes my energy.

However, I still get sucked into arguments and most recently this happened in LuxLuthor's thread L2==>M4==> ? M6 Help a new member right around post #38 with Luna and his badgering about the 65 percent figure. (Not that I was faultless in these exchanges--far from it; check out the actual exchanges and judge for yourself).

So, now to the point --to wit, the evidence:

A smooth, vacuum aluminized reflector with a Welch Allyn 01274 lamp potted into it was sent to an integrating sphere to be measured for total beam lumens, or MSCP (=total lumens/4 pi). This lamp is rated at 553 lumens at 7.2 volts. 7.2 volts was applied at the pins and 391 lumens was measured in the sphere.

391/553 = 70.7 percent.

However, this was the lamp module only. Add in a lens and angular losses due to the lip of the reflector being recessed down into the head of a light and you probably have at least another 5 or 6 percent. Plus, if you consider that an OP or stippled reflector means more internal reflections of the light versus a smooth reflector, then you maybe have even more losses, but how much I couldn't say. But in any case, you end up with something close to --wait for it--

*65 PERCENT*

Taking a step back, I will readily admit that this is only a single piece of integrating sphere evidence. However, it still carries a lot of weight even so.

What really annoys me about all of the recent turmoil over this is the notion that if you don't have an IS, you can't say anything at all. I believe that our ingenuity and inventiveness here at CPF have proven otherwise. From the lumens estimator box, to our very own PaulW :bow: :bow: :bow: and his ceiling bounce tests, we have shown that there really is something in between an arbitrary, off the cuff uninformed random guess, and hard numbers from an integrating sphere.

So it's time for people like myself and Ginseng and PaulW and bwaites to pat ourselves on the back and do a little victory dance and (maybe) say "I told you so."

I would never do this, of course, being far too mature. *cough* I told you so! *cough*

Hmmm? What? Oh, no, I didn't say anything. Just a bad cough. Sorry. :devil:


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## Ginseng (Feb 6, 2006)

Well, at least for me it feels like a huge monkey has just been knocked off my back. PaulW was indeed the first person to present data suggesting the 65% figure and I have my PM's from several years ago to prove it. So to Paul, I would say that "well done!"

Wilkey


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## Ginseng (Feb 6, 2006)

Oh, and Jim, your tenacity and rigor has never ceased to amaze me. Nicely done.

Wilkey


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## bwaites (Feb 6, 2006)

Ginseng!!!

The master returns!!!

Very nice work Jim!!

Nice to have the empirical data to back up the long standing subjective evidence that we have been using.

Couldn't really be much better or closer.

I think flashlightlens.com quotes transmission as 98%, so knock of 2-3% and then an amount as necessary for the recess and js's numbers look close to perfect!!

65% is so close as to be the de facto standard!!


Bill


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## PaulW (Feb 6, 2006)

*Bill.* Yeah, it's fun to see measurements support previous work. That would happen sometimes in my lab classes, although I have to admit there was a bit of fudge in my lab notebook in those days.

I hadn't thought that the 65% figure was a big deal. But you've stuck with the message. In reading some of those threads that discuss this, I learned that the figure can be important in estimating how much real light a planned project will emit. So it's a useful number for those that are _willing_ to use it.

*Wilkey.* Great to see a post from you. I'm glad you're dropping in every now and then. I think of you and the Aurora2 often. 

I haven't looked through those old posts but, as I recall, I never did glom onto the 65% number; I just presented raw data showing that SureFire lumens and calculated bulb lumens were different. I think it was Bill and Jim who gave life to the difference and the number itself.

Paul


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## KevinL (Feb 7, 2006)

Ginseng :thumbsup: 

js: thanks for the proof. My take these days is that I let people believe whatever they believe. We haven't even gotten to talking about Surefire's ratings and their midpoint voltage, which they are rated for. A Surefire with fresh cells or even lithium ion cells puts out a lot more light than it's given credit for.


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## Ginseng (Feb 7, 2006)

PaulW said:


> *Bill.* Yeah, it's fun to see measurements support previous work. That would happen sometimes in my lab classes, although I have to admit there was a bit of fudge in my lab notebook in those days.
> 
> I hadn't thought that the 65% figure was a big deal. But you've stuck with the message. In reading some of those threads that discuss this, I learned that the figure can be important in estimating how much real light a planned project will emit. So it's a useful number for those that are _willing_ to use it.
> 
> ...



Hi Paul,
I actually carried out the final operation of calculating ratios from the data that you presented. So you're right, you did not publish the figure but it was just one step away from your raw numbers. You're also right that it is a useful figure for practical purposes. However, some people will always prefer to quote "crank horsepower" rather than "wheel horsepower" and that's fine, as long as the basis for comparison is equivalent.

BTW, let's get together for sushi sometime. I've had more philosophical investigations and I'd love to hear your perspective on a few things.  

KevinL,
Wow, your ROP as become a legend! Very well done my friend.

Bill,
I see the USL is still trooping along. Man, you've got a lot more stamina than I have, that's for sure. 

Wilkey


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## NewBie (Feb 7, 2006)

js said:


> Now, I was one of the people who inherited the 65 percent figure. I did not derive it myself, but rather was given it by Ginseng, who suggested that it was more or less the best we could hope for and was in his experience as accurate as possible given our limited measurement capabilities. I am told that PaulW was the first person to come up with this rule, and also that NewBie/Jarhead did some calculations and basically said "Yup. That's about right."




Wow, you actually remember my post? OMGOSH!

What I get a kick out of these days is folks using the 25C die temperature lumen ratings on LEDs, and then claiming that on their flashlights, for lumen numbers....

Very nice js, thanks for doing the hard work.


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## js (Feb 7, 2006)

Hey everyone, thanks for posting!

If anyone wants to post the links to some of the groundbreaking threads (e.g. NewBie and PaulW and Ginseng), that would be great.

One thing I also wanted to bring up was something PaulW said to me at one point: he said that in his opinion the 65 percent figure was probably more reliable than the re-rating formulas themselves. And I think that is a very insightful observation.

In this case, the lamp module being tested was being driven AT exactly the rated voltage, so the re-rating formulas don't come into play. But when you over- or under- drive a lamp relative to the manufacturers ratings, then you must use the re-rating formulas. An ohmic approximation is just plain wrong. A heated filament is just about THE classic non-ohmic resistive element. It is the proverbial non-ohmic resistor, in other words. The steady state resistance is a function of the drive voltage, and is NOT constant, not even over a smallish range of voltages. Obviously, if you take a small enough range, then you can use an ohmic approximation, but that range is too small to be useful in modding work.

So you must use the re-rating formulas. These are as follows:

Ir = (Va/Vd)^0.55 * Id
Cr = (Va/Vd)^3.5 * Cd
Lr = (Vd/Va)^12 * Ld

the sub r and sub d mean "re-rated" and "design". I is current, L is hours of filament life, and C is Lumens or Mean Spherical Candle Power (MSCP), which is Lumens / 4 pi, or about equal to lumens / 12.5. If you use Lumens on one side of the re-rating forumla, you must use lumens on the other side.

OK. So take the ever popular Welch Allyn 01111-u, which by the way, was first used here on CPF by Ginseng, IIRC. It is rated at 6.0 volts, 3.35 amps, 464.95 lumens, and 100 hours of life. At this drive value, the heated filament has a resistance of 1.791 ohms (voltage / current).

Now, push it to 7.2 volts. The re-rating formulas will yield the following:

7.2 volts, 3.70 amps, 880 lumens, 11 hours of life.

However, pretend that the resistance stays constant at 1.791 ohms. The ohmic approximation predicts the following:

7.2 volts, 4.02 amps, ??? lumens.

Now, I have EXTENSIVE experience driving the 1111 at and around 7.2 volts, and I have measured current vs. voltage, and I measured *3.68 amps* at 7.2 volts, which, as you can see, is more or less exactly what the re-rating formula predicts.

The ohmic approximation is just plain way off.

Before a certain CPFer attacked me for using the re-rating formulas, I would have thought that they were so well established as to be common ground here on CPF. But I learned that that was not the case. So I have inserted this post to the thread to support the use of the re-rating formulas.

Back to the main point, however: the re-rating formulas are only approximate, and the farther you take them from the design voltage, the less accurate they probably are. ESPECIALLY the hours of life re-rating formula. That has got 12th power in it, and is HIGHLY non-linear. If you are pushing lamps right to the edge, the re-rating forumlas are not going to be accurate enough. For example, both the 1111 at 7.2 volts, and the 1185 at 10.8 volts are supposed to have 11 hours of life (12 in the case of the 1185), but the 1185 on 9 (10.8 volts nominal) cells is MUCH more prone to flashing than the 1111 on 6 (7.2 volts nominal), all other factors being equal, such as the potency and capacity of the cells, and their state of charge. Plus the 1185 has a shorter life span there as well, than the 1111 on 6 cells.

As a rule of thumb I would say that when you go more the 15-20 percent away from design voltage, or if you get into sub 15-20 hour life spans, take your results with a grain of salt, especially the hours of life figure.


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## SilverFox (Feb 7, 2006)

I have been involved in testing for a number of years. There is always a bit of a celebration when the theoretical numbers actually match the numbers as tested.

I have always found it easier to celebrate a close correlation, than to comment on the possible sources of inconsistencies.

At any rate, this qualifies as a time for celebration... 

Tom


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## Lurveleven (Feb 7, 2006)

Great work Jim! Good to see theory and reality coming together.

The reflector you were using, can it be compared to a 15mm opening reflector or 8mm opening reflector? I assume the latter so the 15mm opening reflectors most are currently using will probably have less than 65%, how much is not good to say, but I think it will be best to use 65% for both types of reflectors to reduce confusion.

Sidenote:
I have found the geometry of the beam to be more important than the lumen number. The Gen4 TL LA is a fine example of this, it has the same lumens as Gen3, but it gives you a much better light than the Gen3. For flood lights I can see the lumens number may give a very good indication of the performance of the light, but for throwers I think it should be used cautiously.

Sigbjoern


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## Kiessling (Feb 7, 2006)

:thumbsup:
I love it when my pessimism about true output is correct :green:
bernie


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## litho123 (Feb 7, 2006)

Excellent work Jim - 

When I first joined CPF, the arrival at 65% light loss was one of the threads (amongst others) I copy/pasted into a word document to keep for reference. The posters names were removed so I don't remember who posted the data, but the analysis was very insightful.

It's nice to have it reconfirmed via another means.

The threads which I find most insightful are ones like this one which expand the knowledge base. 

Everyone who has posted in this thread so far, has made contributions which have increased the knowledge of many, me included.

I wish more people would take the time to review the wealth of information that exists here on CPF. Doing a "_thread started by_" search plugging in any of the above key folks will get you started on a reading adventure.


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## bwaites (Feb 7, 2006)

Though I have posted on CPF literally THOUSANDS of times now, I KNOW that it wasn't me who came up with the number!!

However, with all the lights I have looked at in the last 2+ years, I became convinced that the number was close enough that it made sense. 

Having read literally EVERY Ginseng and js post, as well as most of Litho123's, PaulW's, Newbies, and Silverfox's, (I still do weekly/biweekly searches of the names to make sure I don't miss any), I became almost certain that the number was so close as to be essentially the same.

The empirical evidence makes me very happy with the data we gathered with much less sophisticated gear and our own eyeballs!

I still am interested to see how the Light Meter testing turns out, but since almost all my lights, (and all that I design) are hotwires it means less than if I was doing the colored light thing. Most of them are reasonably close on the white lights, (with a few outliers, admittedly). 

Bill


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## PlayboyJoeShmoe (Feb 7, 2006)

I have nothing ground breaking or earth shattering to say here. But....

I THINK a small hole reflector puts a BIT more out the front....

And whatever my M*g85, M*g74 etc. REALLY put out, they are dang bright to me!


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## andrewwynn (Feb 7, 2006)

Really nice to have some I.S. data to back up the renowned figure of 65%. I will continue to use the .65 fraction.. and btw.. my Mag100 figures do include the 65% calculation.. the osram 64625 calculates to 3000L at 12.9V.. and i believe that lamp can actually be pushed to closer to 13.5V... which will bring the output up to 3500L.. (5300 bulb lumen!).. 

I nowdays most often put the lumen rating like so: 

The Mag100 i have sitting next to my keyboard right now is dialed into 13.2V which means it generates 3909/2541 Lumen. 

It is extremely confusing to read a description of a lamp that says it is an '880L' lamp or a '700L' lamp.. when those numbers are re-rated to battery voltage and not factoring in resistive losses (the particular "700L" lamp, which is unnamed to offend as little as possible esp. since it's one of my absolutely favorite lights.. ACTUALLY is closer to 491/319 in stock configuration.. and even with a KIU kit it's 547/347. 

I did a lot of learning about how much output is affected by slight voltage changes, due to resistance, and was fairly quickly introduced, probably by JS to the conversion factor here.. 

Thanks for the update and going through the effort to get a known light into an IS.. very nice.. and good to see all these times we've been on the right track. 

Oh.. esp. with the fact that SF does rate (conservatively i might add) with torch lumen.. my estimate was over 600L with the SF M6 i was working on.. it had more output than my M66 that is generating 900/585L... at least initially.. maybe the 500L is to consider average over battery life or something.. nice to see a company use conservative values and also to use the 'out the front' output and not the bulb values. 

Originally i only used bulb values because that is what is being generated and what can be calculated.. but now, esp. with the hard-evidence.. so can 'torch lumen' as well.. the problem i'm seeing.. is that I believe that the reflector size is directly responsible for a signficant portion of that efficiency.. so.. maybe with a mag reflector it's 65%.. and maybe with the 3" reflector it might be 70.. even 75%.. it would be very nice to know what ratio to use for bigger reflectors.

That said, thanks once more for your solid and continuous input to improving illumination, Jim. 

-awr


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## NewBie (Feb 8, 2006)

js said:


> Now, I was one of the people who inherited the 65 percent figure. I did not derive it myself, but rather was given it by Ginseng, who suggested that it was more or less the best we could hope for and was in his experience as accurate as possible given our limited measurement capabilities. I am told that PaulW was the first person to come up with this rule, and also that NewBie/Jarhead did some calculations and basically said "Yup. That's about right."




If anyone ever finds that thread in the archives, I'd sure appreciate it if you'd PM the link to it!

I sure miss the search function *alot*. There is such an incredible amount of information posted here on cpf that for all practical purposes is now gone (not searchable).


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## js (Feb 8, 2006)

AWR,

Oops! Sorry. I actually wondered about that the other day. I'll edit my post to remove that reference. Thanks for your post!

Lurveleven,

The reflector was actually a Gen2/3/4 TigerLight stock reflector, which has an inner bore, IIRC, of about 12 mm, so it is right in between the 9.6 mm Carley stock 1940 bore, and the 15 mm Mag pedestal compatible bore. Oh, and so this was a 2" diameter, smooth surface, fairly tight parabolic reflector.

I'm going to see what kind of a deal I can get on 3 or 4 more tests, and I'm thinking of testing a couple 1940 with two different ring-potted WA lamps installed (1160 at 6.0 volts and 1111 at 7.2 volts probably)--and this would test the 9.6 mm bore--as well as a Carley 2102 3" reflector (with same bore), as well as maybe a SureFire M6 with MN20 installed, or a SF M6-R with MN21, and maybe an A2.

But it all depends on how much it will cost. I'm just toying with the idea at present.

As for the note on beam profile which Lurveleven mentions, I am right on board with that. A lumens total is only one part of what a beam is, and for some beams, it really doesn't tell you the whole story. The Gen4 TL LA is a great example of this. It is "only" about 275 lumens, but I just love that beam. It is far more powerful than the lumens total indicates.

But still, a lumens total is good information to have, and if we're going to talk lumens, we might as well talk sensibly about them (i.e. use the correct conversion factor for a more realistic estimate of what comes out the front of the light.)


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## MSI (Feb 8, 2006)

AWR,
regarding 2" vs 3", I don't think you will get better efficiency with the 3". I think it actually will be less. The reason I think this is because you will have a larger reflector area that means you will have a larger area that "steals" light. But will there be a significant difference, I don't think so, and the difference would also have to be pretty large for anyone to notice in a ceiling bounce test. However, even if the 3" should be less efficient it will stomp all over the 2" when it comes to throw. This is another example that lumen numbers should not be used blindly.


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## Ginseng (Feb 8, 2006)

I had removed the opening posts of many of my informational posts so that I could update them. Unfortunately, I have found that the time to update them never really materialized. So, over the next few days, I will reinstate those posts. I will also look for Paul's landmark thread. That is, if someone else doesn't find it first.

Wilkey


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## js (Feb 8, 2006)

MSI,

I suspect that you are right on about 2" vs. 3" reflectors.

NewBie,

Here is one of PaulW's threads: 500 Lumen Mag 3D and this may be the one from which Ginseng calculated the 65 percent figure.

It's truly interesting, because if I understand things correctly, the ceiling bounce test calculations are for an 1185 being run from 9 AA's. We now know that the A2 is really right around 75 lumens, and not 50 as it is quoted on the SF website. Using 75 instead of 50 yields 785 torch lumens for the 1185 on 9 AA cells, which is very close to what we now consider an 1185 light to be, using 9 decent AA cells.

Neat, neat, neat. Who says a ceiling bounce test is worthless? Not me, that's for sure.

But this, I think, is the jack pot of historical threads related to the 65 percent figure: Performance of Bright Lamp Configurations.

Enjoy.


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## Luna (Feb 8, 2006)

andrewwynn said:


> Really nice to have some I.S. data to back up the renowned figure of 65%. I will continue to use the .65 fraction.. and btw.. my Mag100 figures do include the 65% calculation



Yes it is. This is good validation of my questioning of JS as to if the numbers have been tested.

It is a good safe number but you still have the situation where the 65% may be too low, like: the newer reflector with decreased bulb opening (~8% calculated), better glass 5-6% , aa larger reflector, Enhanced Al coating (8-10%). Of course these are individual numbers of each component alone, so the increase in the transmission line eff% will not be so great.


I just caution the assumption 65% is a catch all. This rule of thumb only applies to basic bulb-~2inch reflector(standard profile, not deep or shallow) combos. Optics and even LED-reflector combos will be different. 

I'd still contend that nobody should advertise with this assumption alone, testing is imperative. 65% is only a predictive coeff (except in the given test case), not concrete in a jihadish sort of way 






MSI said:


> I don't think you will get better efficiency with the 3"



I 'think' you would. Here is my reasoning. A large portion of the losses are from 3 sources: backplane absorption (the hole), internal reflection and reflection back to the bulb. The hole is a given so write it off or silver the glass envelope under the filament (hint hint) 

Now a reflector with the same depth will have a lesser amount of incident losses because less light will reflect back to the source or rereflect back to the reflector due to the changed geometry.


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## js (Feb 8, 2006)

Also,

A third thread by our own renowned PaulW is Lumens Estimates for Aurora2 & Mag85 and is well worth checking out.

Actually any of PaulW's threads are well worth checking out. As well as any of Ginseng's threads and bwaites's threads and NewBie's threads and McGizmo's threads and Illuminated's threads, and so on and on and on. Very few people seem to realize what was just point out in a post above: the search function works great for finding threads and posts of a specified person. Just type in their username and if you want threads select "Threads started by user" and if you want posts, select the other one, and you can display post results in the form of individual posts or threads. Unfortunately, a lot of good stuff is hidden away in unlikely threads started by unlikely people, so it still is painful not to have the search function. But still, . . .


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## bwaites (Feb 8, 2006)

Actually, the reflector tested had NO back opening, but a white potting compound in the hole.

The losses would have been LESS than a small hole, because the white is reflective.

The 65% figure is a close estimation, nobody I have seen has EVER posted it as a hard and fast figure. 

I'm willing to bet that the number doesn't vary much, regardless of the size of the reflector, *SO LONG AS THE COATING IS THE SAME*. Different coatings will change that number somewhat, but metalized, vacuum coated reflectors as used by us will be close to the same.

Larger reflectors will collimate (sp?) the beam more effectively, but I bet there isn't much different in the losses depending on size.

Newbie probably has a way to show that using his knowledge of optics and equations, but it is over my head.

Bill


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## js (Feb 8, 2006)

Luna said:


> Yes it is. This is good validation of my questioning of JS as to if the numbers have been tested.
> 
> It is a good safe number but you still have the situation where the 65% may be too low, like: the newer reflector with decreased bulb opening (~8% calculated), better glass 5-6% , aa larger reflector, Enhanced Al coating (8-10%). Of course these are individual numbers of each component alone, so the increase in the transmission line eff% will not be so great.
> 
> ...



Luna,

Did you actually read my post(s) above? Because,

1. This module which was tested had no glass in front of it at all. So my 2 percent reduction subtracted from the 70.7 percent due to it was probably on the low side. Thus there is no way to gain 5 percent due to the glass.

2. The reflector *DID have* the "enhanced aluminum coating", otherwise known as vacuum aluminizing, so there is no better coating that would increase the results by 8 to 10 percent.

You caution us all, do you? We shouldn't "advertise" based on the 65 percent figure? This "catch all" rule of thumb applies only to approx. 2 inch reflector that is not shallow or deep? The 65 percent figure shouldn't be applied in a religious-war kind of way?

Luna, who's doing that? Show me the place where it was ever anything BUT a rule of thumb.

No "thank you, js, for providing this info" but instead a "Yes it IS good to FINALLY have a real answer to MY questions--*BUT* . . .

Always the tearing down and picking apart. Always the badgering, poking, proding, arguing. Talking about how a hotspot can easily "hide 100 lumens" in a ceiling bounce test. In fact, aren't you the same person who said that a ceiling bounce test was worthless for determining a lumens total? And yet, here we have a confirmation of results originally gleaned from inventive ceiling bounce tests.

Aren't you the same person who said that an ohmic approximation was good enough for our use in this thread? And yet, it is easy to show that it is not.

Given that you called me an asshole on our last exchange, questioned my motives, educational claims, method for approximating the MN21 current (which by the way was for an *upper bound* so that the assumption of 100 percent LVR efficiency was actually moving the result in favor of your position of a higher draw current--but you never understood my reasoning in the first place, did you?) --

given all this, can you be surprised that I am really not impressed or concerned with the cautions and reservations and limitations you would like to impose on us all?

And who the hell is "advertising" anything anyway? We are just a bunch of amateurs trying to have fun and trying to do the best we can with what we have. If someone is willing and interested in making an estimate of the torch lumens of his light, where's the problem?

Although, look, if you want to start offering free integrating sphere tests at a cost to you of $125 a pop, then fine. Then you can say that testing is "imperative." In fact, why don't you do that--drop some cash on IS tests--then post your own, more complete thread on transmission efficiency. And then I'll post to your thread, OK?

It's posts like yours that really REALLY make me consider NOT sharing my information here on CPF at all. Tell me, what have you offered in the way of positive contributions here? Nothing that I can see except to qualify and limit everything that this thread is about.

Because, this thread is all about (or should be) the notion that we can do the best we can with what we have and a good helping of ingenuity. People like PaulW and Ginseng are ingenious and inventive enough to come up with a method for approximating the real output of our incan mods and all you can do is to try to tear it down. Talking about all the many reasons why it isn't valid, or is only valid in this one particular case and on and on.

I am perhaps being unwise in posting this in anger --because I AM angry at you and have been since the last thread where we crossed paths-- but at the moment I don't care and would much rather get these things out. I may regret it later, of course. We shall see.


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## Luna (Feb 8, 2006)

What? 

JS, are you unable to carry on a discussion in an adult manner? You send me a PM that you will never participate in a thread that I'm in and wished me to not ever contact you again. You now call me out directly in a post and do so with the closest impersonation of my 7 year old niece saying 'NeeNeerNeeNeer' .. .


My post was not in the least critical of you, I was taking to Andrew about advertising. Gees, like I said, what an ***.




*#1: *
You measured 70% and applied the losses of the glass and lip to get around 65%. I was reading your post.

*#2: *
Silvering and enhanced AL are not the same as vacuum aluminizing and both are greater in reflectivity on average. vacuum aluminizing with a non dialetric (standard al coating) will yield ~>85%, enhanced Al >93% and Ag >95%(initially)

Vacuum Al, doesn't mean it is enhanced.





> "which by the way was for an upper bound so that the assumption of 100 percent LVR efficiency was actually moving the result in favor of your position of a higher draw current--but you never understood my reasoning in the first place, did you"



Huh? I haven't a clue when we discussed this or how it has anything to do with this thread. If talking in reference to the Mag60 vs the M6 again, then you have a poor memory. How many time did I say my only **question**, not statement , was the blanket assertion of the eff%. I however said the M6 is too expensive for a simple device.
...


Finally,

Look JS, if you wish to used the 65% for TIR, optics and LED based system go right ahead. I just wouldn't use the 65% for atypical. I'd imagine Newbie would concur with this particular assertion.

It would be like comparing the gas mileage of a hybrid and a SUV as being the same because they are both vehicles.


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## Luna (Feb 8, 2006)

PS,

JS, most of the issue that you mention like paul's stuff were items that you assumed I attacked. I never did...I just asked if you had proof of 65 or if it was off the cuff. You now have proof. Why is it so hard for a person to ask a question or participate? You love to attack people's numbers, is it so bad that someone ask you about yours?



> In fact, aren't you the same person who said that a ceiling bounce test was worthless for determining a lumens total?



No, I've even quoted my ceiling bounce number before we ever spoke


----------



## Luna (Feb 8, 2006)

bwaites said:


> The losses would have been LESS than a small hole, because the white is reflective.



Understood. Reflective, to what degree? Id assume the potting wouldn't be too effective but I haven't a clue as to how much so.


----------



## bwaites (Feb 8, 2006)

Short of a mirrored finish, white is the most reflective "color" out there, reflecting the full spectrum of light.

Trying to quantify it in so small a usage is ludicrous.

No one implicated that using the 65% figure was good for anything but a flashlight reflector, not TIROS, optics, or anything else.

However, an LED in an efficient reflector is not MUCH more efficient than a lamp, so I'm more than comfortable using that same 65% figure for REFLECTOR based LED lights.

As for your problem with js, it appears that you do all you can to antagonize him. 

So far as I know, every metal reflector used by anyone on CPF is using vacuum metalization over aluminum. They all have essentially the same reflective profile. Higher reflectiveness is only in comparison to other reflective coatings, so a 10% gain in reflectivity vs standard aluminum coating is NOT equivalent to a 10% gain out of the reflector.

Nevertheless, the best estimate, confirmed by early testing, is that a normal, vacuum metalized flashlight reflector pushes about 70% of the light produced by a normal lamp out the front of the reflector. Approximately 5% of the light produced and reflected outward is then lost to the window (lens) and bezel of the light.

'Nuff said!!!

Bill


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## Luna (Feb 8, 2006)

> Short of a mirrored finish, white is the most reflective "color" out there, reflecting the full spectrum of light.
> Trying to quantify it in so small a usage is ludicrous.



All I said in the post you replied to was, mirror the bulb on the backside to minimize backplane loses. What is the problem? We said the same thing





> No one implicated that using the 65% figure was good for anything but a flashlight reflector, not TIROS, optics, or anything else.



And that is all I said! What is the problem? We said the same thing




> However, an LED in an efficient reflector is not MUCH more efficient than a lamp, so I'm more than comfortable using that same 65% figure for REFLECTOR based LED lights.



Difference is that an LED like a lux is lambertian so backplane loses are already accounted for. In freespace they never radiate backwards due to the emitters topography. In this case the distribution pattern affects the losses.
You can put a mirror behind a lux and the IS result will still be about the same as having it in freespace. Do the same with a bulb and the results will be much different.




> As for your problem with js, it appears that you do all you can to antagonize him.



His first post to this thread mentioned me so I came.(and another one in a around about way. You recognize that I hope




> So far as I know, every metal reflector used by anyone on CPF is using
> vacuum metalization over aluminum. They all have essentially the same reflective profile.



These same 65% figures are applied here for a Al film here on CPF too . Given the deep wallets about, I wouldn't be surprised to see people buying enhanced reflectors in the near future on CPF. Hence the simple mentioning and cautionary note. It wasn't critical of anyones contribution, just a simple statement. Once again we agree: typical components realize typical performance. What is the problem? We said the same thing




> Higher reflectiveness is only in comparison to other reflective coatings, so a 10% gain in reflectivity vs standard aluminum coating is NOT equivalent to a 10% gain out of the reflector.




Of course not, did you read my initial post to the thread._ Of course these are individual numbers of each component alone, so the increase in thetransmission line eff% will not be so great. _ What is the problem? We said the same thing


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## Luna (Feb 8, 2006)

One last point, taking a bit due to all of your hidden attacks

* QUOTE:*The ohmic approximation is just plain way off.
Before a certain CPFer attacked me for using the re-rating formulas, I would have thought that they were so well established as to be common 

ground here on CPF. But I learned that that was not the case. So I have inserted this post to the thread to support the use of the re-rating 

formulas


Ohmic approx was used because you never provided *us* with the current at the baseline until after the fact. You told us the rerated 

parameters and that the filament was near mealting as per Willie.

The ohmic approx is sufficient in this case but the both current and voltage measurements would have been better. You finally provided it and 

guess what, it was appreciated. It just so happened that my measurements (and approx) yielded a measurement closer to brocks, not your guess.


I even gave the formula for determining the tungsten filament resistance.

*

T = -1.86(R/R0)^2 + 206.6(R/R0) +118

R= resistance of filament at temp
R0=roomtemp(0 really but no need to freeze it)
*

When the filament temperature is already in the 2800K+ range and the Tdelta is very low it approachs ohmic behavior . When the gradient is 

large, it is classical nonohmic. If you can derive the resitivity at a particular temp, the change in R can be derived via the diffeq at the 

new temperature. You provided the temperatures/color temp.



* QUOTE:* People like PaulW and Ginseng are ingenious and inventive enough to come up with a method for approximating the real output of our 

incan mods and all you can do is to try to tear it down. Talking about all the many reasons why it isn't valid, or is only valid in this one 

particular case and on and on.

I take it you missed my post last year outlining use of a digital camera,photoshop, ceiling bounce and a light of known output to derive 

light box type of lumen estimates. I try to contribute to yah know...

march 9 2005 
_
...I did one step more. I did a ceiling bounce with a white door being photographed in manual mode. I used a p60 with new batteries for 

reference, the l2, u2 and u2 + l2.

I did a 25x25 point sample at a point in each picture to derive the rgb. I summed the components and applied a ratio to the known approximate 

output results. 

P60=1*65lumens=65 lumens (hard math) (22 was the r+g+b score)

L2 rgb score =33 33/22 * 65 = 97.5 lumens
U2 rgb score =41 41/22 * 65 = 121 lumens
u2+l2 rgb score =78 78/22 * 65 = 230 lumens

Of course there is error in the ccd due to the bayer filter and other issues. The system isn't technically sound but is isn't a bad estimation 

assuming the p60=65lumens was a good calibration. So the simple test does help to back my claim of the difference between the two. 

I'd imagine I can make it work better, including giving spectral results but it was more of a verification. I need to do the same without he 

B65 battery and also the 3x123 u2 which seems to give about a 20lumen increase (just a test not a long term burn because I like the u2 and I 

only have 3 levels vs 6 when doing this) 
_


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## js (Feb 8, 2006)

Sorry Luna.

You're right. I suppose I did call you out in mentioning the LuxLuthor thread, and that you were thus more or less obliged to make an appearance here, even though I did say in a POST (not a PM) that I was done with you.

And yes, while sometimes I can carry on an adult conversation, there are other times I fall short.

As for the 100 percent LVR efficiency, I am refering to this from the same SF/M6 thread I linked to above in the "this thread" hyperlink:



Luna said:


> So you believe an ohmic "approximation" is not suffient here when dicussing a current a small temperature change. Oh well lets jump to emperical then.
> 
> I just measured the MN21 with 2 LG2400s(used a bit but with open terminal voltage of 7.98--full charged normally to 8.32v)
> 
> ...



I went to a lot of trouble to make that post wth the "farout" assumption in it, which, by the way is only 2 percent away from the truth, and I did all of this *because you asked me questions*. And the thanks I got was for you to argue with me over extremely well established re-rating formulas and to belittle my post which attempted to come up with a current draw based on the information I had to hand at the time.

You can say I am an *** if you want, and there are certainly situations where I have made a-hole type posts, but in that thread I was only trying to be helpful and to answer the questions asked of me. And for the record, what I said to you in a POST was the following:

"And you know what else, Luna? I'm done with you. Don't PM me and don't post asking me any questions any more. And I sure as hell won't bother trying to post to any thread you're involved with."

Except of course my own threads, because how can I not be involved with my own threads?

So, speaking of my own threads, let's move on, shall we? To some constructive and helpful discussion.

For starters, I remember reading a lot of stuff about optical coatings in NewBie's Reflector coatings and in the visible range, I remember aluminum being pretty much the best, but it's been quite a while.

Maybe someone can speak more or less authoritatively on this subject for our benefit? NewBie maybe?


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## tvodrd (Feb 8, 2006)

(Jar- give 'em hell!)

Larry


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## andrewwynn (Feb 9, 2006)

I have noticed something when doing ceiling bounces.. The RT4 light which is supposed to be aprox. 440L.. actually estimates over 400 TL, so i think there is something to that 65% not being the right factor when considering LEDs.. Has anybody else done some simliar comparisons? 

-awr


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## NewBie (Feb 9, 2006)

tvodrd said:


> (Jar- give 'em hell!)
> 
> Larry




Well, I'm a working man, and I've gotta head out early in the morning, so I will try and keep things very brief.

For now, IMHO, the generic 65% is a great way to hit a rough approximation.

If someone wants to use another number, I do feel that an integrating sphere is going to be the only real legitimate way of claiming otherwise.

Don't forget that AR coated lenses range from 0.2 to 2% reflectivity on each surface (front and rear), depending on whether it is a single coat, or a multilayer broad band coat. The skill of the chamber technician will affect the final outcome. You also incur losses in the glass lens, depending on whether it is common soda lime, "water white" (soda lime with reduced iron), borofloat, or various other types of glass. There are also two common types of AR coatings, Magnesium Fluoride and Silicon Dioxide. The Magnesium Fluoride coating typically will have a lower reflection amount, but the Silicon Dioxide is a bit tougher. Usually a good Silicon Dioxide AR coating will look green when done correctly, and you can judge the quality of the Mangesium Fluoride coating, as it should have a purple hue or tint in the reflection. Having the coating thicknesses done just right, means it is centered in the visible band, and you get some reflection on the red side and some off the blue side, with the least in the center (green). Thus the purple hue.

**BUT** AR coatings do not work as well when the light doesn't hit the surface perpendicular. As the angle increases, the percentage of reflection increases very significantly. This is something to take in account for if the diameter of the opening increases without increasing the depth at the same time.

As far as the effect of the rear hole, the reflector focal point would have a good amount of effect. In most reflectors, the bulb itself takes up a considerable portion of that "escape" area anyhow. If that escape area is further filled with a mirror, or even a white ceramic or whatever, it's contribution will be even less. Though one would really have to wonder, if it wasn't directing the light out the front, what real good those few lumens would be. Consider the area of the gap, or the "escape area", it's distance from the filament, create a sphere around the filament at that distance, and compare the area of the sphere to the gap/escape area (and remember not to include the area the bulb itself blocks)...

It would be a pretty trivial task to stick all this into a decent raytracing program and assign all the surface properties, and then re-run it with new propertes. It just takes time, which I do not have at the moment.

The reflector coatings are an important piece of the whole situation. Though I don't know if I'd personally buy just an Enhanced Aluminum, or Enhanced Silver. I'd be more apt to lean towards a protected enhanced aluminum or protected enhanced Silver. I did several posts on these coatings in the 2003-2004 timeframe, complete with quite a few links to references.

Boy, I sure wish the search function still worked, there is an awful lot of wonderful information we built up over the years. These special reflector coatings are nothing new, and we have discussed them several times before.

Unfortunately, standard Vacuum Deposited Aluminum is not quite the same as Enhanced Aluminum, though it usually is better than no coating. Additionally, I've seen multilayer stackups of various materials, that can attain +98% reflectivity, even with the Silicon Dioxide protective overcoat. Think of it kinda like a dichroic reflector, but used to further enhance the coatings even more.

Again, IMHO, the 65% is a *darn* good number to start with, until a given item is actually tested with an integrating sphere. At that point, with real numbers in hand, then one would be able to legitimately claim otherwise for that particular setup.

Oh, and on the ohmic thing. Doesn't the formula only figure for a filament in free space? One would have to consider the contribution of putting it in glass envelope, pumping it full of a gas, and the heat it would contain, as well as the contribution of cooling since there is a gas in there, and the air currents. One might want to also figure in the effect of the stand off wires to the whole situation. I've never seen the source for the formula, nor bothered to look up how it was produced. I'd also figure that how the filament was wound, single turn loop, single turn loop then wrapped in a larger loop, and the proximity of the other turns in the loop, as they'd radiate into each other. Also, something that comes to mind, is the halogen cycle... Now, once you contain all this in another housing, such as a reflector with a cover glass on the front, you in essence have formed yet another thermal containment chamber of sorts.

Just my quick thoughts on things, I really gotta hit the sack now, you guys have a great night, and even a better tomorrow.


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## LuxLuthor (Feb 9, 2006)

I wish I knew as much about all these technical aspects as those speaking in this topic, but it was interesting reading from all parties....even if I only picked up some of what was being said.

Great topic, even with the :touche:


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## js (Feb 9, 2006)

NewBie,

Awesome post! Was the thread of yours I linked one of the ones you were thinking about?

Larry,

Don't egg me on, man! I'm already too prone to that sort of thing as it is!!!

AWR and everyone else,

I thought it was obvious from my choice of forum for this thread (Incandescent) and from the PaulW threads I linked, and from my initial post, BUT, just to be clear:

***I only know about ican mods and *I am only recommending the 65 percent figure as a good rule of thumb for INCAN mods*. If anyone got the impression otherwise, I apologize. I have no idea what sort of conversion factor to use when considering LED's and optics or reflectors. No idea whatsoever.

As for the resistance versus temperature of Tungsten, NewBie's comments are right on. That formula is indeed for a bar of Tungsten in free space. First of all, when you coil the filament, the coils mutually radiate into each other and heat each other up, which is why the center-most coil reaches a higher temperature than the ones on the end. Then put the whole thing in a high-pressure fill gas (of any of various compositions) and throw in the halogen cycle and the relationship between CCT and filament resistance is anybody's guess.

And, I have learned from talking with the Carley engineer who designs their lamps, that measuring and determining CCT is not standardized. Welch Allyn, he informs me, always gets significantly higher CCT's from the same lamps than Carley does. You can even see this by checking out their web pages for xenon lamps and halogen/xenon lamps, then compare the range of CCT's with the www.walamp.com webstore specs for the Halogen lamps. (Click on webstore, click on Halogen, then move through the various pages).

I asked the engineer the question that Lurveleven and myself have been wondering about for many months now: "Why make a xenon lamp and NOT add a halogen to the mix to prevent blackening?"

According to someone here on CPF who used to work at a facility that made halogen lamps, he said that if you want to make the most efficient, highest pressure xenon lamp, you can not add any significant trace amount of a halogen because it will corrode the filament supports at the highest pressures. (I think that's a fair paraphrase).

But when I tried to pin this engineer down on the subject he more or less denied that there was any real reason NOT to add a trace amount of a halogen to prevent blackening over time, but only said simply that "it just isn't necessary" in the lower powered xenon lamps because they don't deposit much tungsten on the envelope anyway.

So now I'm no longer sure about the whole issue of xenon vs. xenon/halogen. And in fact, the WA lamps have a krypton fill which you think would mean slightly less efficiency than the xenon, but yet the WA lamps seem to have the highest efficiencies of any of the available halogen lamps out there, even when considering the SureFire lamps as well. Plus they can do them smaller than almost anyone else for a given power.

I am trying to get my hands on some real engineering manuals for lamp physics and design, but they are apparently almost all proprietary internal documents owned by companies like Sylvania and Osram. Still, the Carley engineer said he could maybe put something together for me. I sure have a lot of questions that such a manual could help me answer.


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## Luna (Feb 9, 2006)

Newbie, hola.

* quote: Newbie*_
As far as the effect of the rear hole, the reflector focal point would have a good amount of effect. In most reflectors, the bulb itself takes 
up a considerable portion of that "escape" area anyhow. If that escape area is further filled with a mirror, or even a white ceramic or whatever, it's contribution will be even less. Though one would really have to wonder, if it wasn't directing the light out the front, what real good those few lumens would be. Consider the area of the gap, or the "escape area", it's distance from the filament, create a sphere around the filament at that distance, and compare the area of the sphere to the gap/escape area (and remember not to include the area the bulb itself blocks)...
_

This is why I think ultimately TIR like optics will be great for incand also. Capturing light from the front and the rear and redirecting it 

forward.

The silvering of the bulb might not contribute too much (hard to say since it depends on the envelopes optical characteristics) but is will 

help some (just like UCLvsLexan or ProGold on the electrical contact etc). If anything is will help reduce backplane absorption which of 

course reduces the warming of the light


So what do you think of my the LED assertionYou alway contribute good, well thought-out information so comments would be appreciated.


(I'll hit the ohmic question in another post)


PS you can do a partial search on google using site:www.candlepowerforums.com and just add any other terms. Be sure to click on the cached 

copy. Then do the profile thing to find the whole thread. I do wish the search was working though.


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## NewBie (Feb 9, 2006)

Can anyone give me approximate reflector dimensions and hole size?
Lamp dimensions for the package, filament, metal base height?
Typical bulb lumens for the bulb?


When I get home tonight, *maybe* I'd have time to model something up, and toss in various surface parameters, and see how the numbers fall out.

Those were not the threads I was thinking of, I was thinking more about the one where I was talking about the losses, as the light travels from the source to the reflector and out, and the other thread where I gave a number of coating reference .pdfs


More info on AR. The multilayer magnesium flouride AR coatings are commonly known as HEA and BBAR. More information on the AR coatings can be found here:
http://www.molalla.net/~leeper/ar_coa~1.pdf

And some generic reflector coatings:
http://www.molalla.net/~leeper/refcoat.pdf

Perkin-Elmer's line was picked up by these folks, and they offer some great reflector coating information and services:
http://www.optiforms.com/4000services/4100opticalCOATINGS/41400ocREFLECTIVITYscience.html

Remember, take bare aluminum deposited coatings with a grain of salt, as they rapidly deteriorate upon exposure to air...


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## Luna (Feb 9, 2006)

*QUOTE:js*_***I only know about ican mods and *I am only recommending the 65 percent figure as a good rule of thumb for INCAN mods*. If anyone got the impression otherwise, I apologize. I have no idea what sort of conversion factor to use when considering LED's and optics or reflectors. No idea whatsoever.
_

No no no no no. I want criticizing your numbers. I just added the LED bit as a point to ponder.


*QUOTE:js*_
As for the resistance versus temperature of Tungsten, NewBie's comments are right on. That formula is indeed for a bar of Tungsten in free space. First of all, when you coil the filament, the coils mutually radiate into each other and heat each other up, which is why the center-most coil reaches a higher temperature than the ones on the end. Then put the whole thing in a high-pressure fill gas (of any of various compositions) and throw in the halogen cycle and the relationship between CCT and filament resistance is anybody's guess.
_

If you know the current and voltage (which you measure), you can use ohms law to get the resistance at each level. Compare it at multiple input levels and you can see that it is *fairly* linear over 2800K (until melting)

Just about all conductive surfaces display a nonlinear resistance over a the range of power inputs. Even plain copper wire, it just isnt as pronounced as a tungsten filament. See below link since you don't want to accept my formula (which is by the way for a filament not a bar)


*QUOTE:js*_
relationship between CCT and filament resistance is anybody's guess
_

CCT correlates well to the filaments temp(IIRC approx 300deg diff in the bulb types we are discussing since hotspots there is a temp gradient involved) . The filament temp directly governs filament resistance though. However, when you said that the data you provided from willie was "with the filament about to melt", we were no longer with CCT but actual temperature. Don't confuse CCT and actual filament temperature as being synonymous. However see below link, they seem to be ok with the concept at sylvania.




http://www.sylvaniaautocatalog.com/new_sylvania/tung_fila_lamps.htm

"Since the temperature coefficient of resistivity for pure tungsten is relatively constant over the range of lamp temperatures, it provides a convenient means for measuring the average temperature of a filament. "


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## js (Feb 9, 2006)

Luna,

Please don't bother hitting the ohmic question in another post. Not on my account anyway. OK? Because it really doesn't matter what the resistance of the filament is. You can always find a single voltage and current point and then use the re-rating formulas from there to determine the new current at a different voltage. It's more or less straightforward to measure the current draw of a lamp for a given drive voltage, then you just go from there. I'm not sure why you even needed it back in that "SF/M6" thread because I *DID* right from the get-go give voltage and current values for the MN21. Then you posted this, a couple posts prior to you challenging me on the re-rating formulas:



Luna said:


> js said:
> 
> 
> > 4.9 to 5.0 amps times 6.8 volts equals 33.3 to 34 watts.
> ...



The ohmic approximation is never going to be useful. It is always just as easy and more accurate to use the re-rating formulas.

And notice that they do not have a re-rating formula for CCT? That's because the relationship between CCT and V, I, Hrs. of life, and Lumens is not deterministic. It depends on fill gas, filament geometry, envelope size, etc., etc. You can reverse engineer one from the various WA specs, but I suspect that that is probably only approximately valid for their lamps only. Because I know that the fill gas alone can have at least a 100 K effect on the CCT.

As for mirroring the underside of the lamp envelope or the surface of the potting material or support structure, I can only say for sure that you obviously have to make sure not to form a conductive path between the two lamp pins, and also that you will probably introduce some spurious light to the beam, i.e. artifacts. Plus there may be some issues with increasing envelope temperature at the pinch, as well as mating the materials together over such a large range of temperatures. It certainly can be done: I know of an Osram lamp, for example, which is meant to hang down from ceiling lumiaries and its bottom half actually IS a reflector. Pretty neat, really.

But anyway, let's just drop the whole ohmic question, OK? I mean, you aren't saying that it would be BETTER than the re-rating formula for current vs. voltage, are you? If not, then the question is really a dead-end in my opinion, FWIW. But suit yourself I guess.


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## js (Feb 9, 2006)

For those who would like to have as complete and authoratative a source as I have yet found on Halogen lamps, go to this Osram/Sylvania page and click on the link that says "Engineering Bulletin - Technology and Application - Tungsten Halogen Low Voltage Lamps Display/Optic." And it will open in a pop-up window (these must be enabled) and start Adobe reader. It's a pretty big file so it will take some time to open on slower internet connections, but once you've got it, you can save it to your own hard drive or whatever.


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## Luna (Feb 9, 2006)

*quote JS*_
And notice that they do not have a re-rating formula for CCT? _
See my sylvania link THEY do! 



*quote JS*_
The ohmic approximation is never going to be useful. It is always just as easy and more accurate to use the re-rating formulas._ 

Like said above, It was used in the absence of the necessary information to use the WA that you cannonize. Your reading comprehension is being affected by your anger. 



---




BTW, I'm not responding on your behalf alone. This a a community so if you wish to discount my contribution go ahead. I'm posting for others too. 

You continue to attack the person not the post. Shall I then? You were wrong on the reflector coating (vac Al <> Enhanced Al). You are wrong on this. You were wrong in the assertion soldering end to end won't cause leakage. etc...

Get over it. This is unproductive. Lets talk so we can all learn something! Set aside your hurt ego. My god man, you are still harboring hate on a post from 2 months ago.


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## wquiles (Feb 9, 2006)

js - great post. As always, thanks for sharing your experience with us :bow:

Will


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## bwaites (Feb 9, 2006)

Luna,

You continue to do nothing productive or enlightening in this thread.

If you would like to discuss whatever topic you so desire, please have the decency to go start your own thread. 

Your posts here have provided NO enhancement, and apart from your constant baiting and sniping do nothing but muddy the intent of the thread. 

I, and many others, apparently, since no one else has even responded to your constant harping, see no need for your continued interruptions. 

As for js being wrong, I see no where that he was wrong on coatings (I stand corrected by js though I am still missing something), no where that anything about soldering was mentioned. (For your information, several large manufacturers offer end to end soldering at a premium for those wishing the least resistive connection for their battery packs. While Jim has stated that the cause for battery failures in the USL project MIGHT be related to soldering, many unsoldered cells have failed, even those purchased and used individually apart from my project.)

You are right about one thing, this is unproductive! You advised js to get over it, I would ask you to do the same, and take your opinions and thoughts to your own thread.

Finally, I am offended by your invocation of Deity, please refrain from similar use in the future!


Bill


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## js (Feb 9, 2006)

Luna said:


> *quote JS*_
> And notice that they do not have a re-rating formula for CCT? _
> See my sylvania link THEY do!
> 
> ...



Luna,

I did get over it. I was responding to your posts and not attacking you or your person. Where did I do that since I said I was sorry and "got over it"? I'm quite sure that I didn't.

And now I really and trully have to seriously doubt that you aren't intentionally trying to make me angry.

Please stop this.

*****

First off, I posted what I did before I had seen your post #40.

Second, it was relevant because you keep claiming that you needed the ohmic approximation because of the absense of necessary information. Not so. And it also points out that the ohmic approximation which you used over the 6.1 to 6.8 volt range was off by a non-trivial amount.

The example I gave above of the WA 1111 at 6.0 volts vs. at 7.2 volts **is* within the range which you claim is approximately linear. The CCT at 6.0 volts is 3325 K, and the CCT at 7.2 volts is probably close to 3500 K. Yet the ohmic approximation yields 4.0 amps, and the re-rating formulas yield 3.70 amps. That is a significant difference.

As for the difference between CCT and actual filament temperature, I am well aware of it and have mentioned it a number of times before this thread. The CCT can be approximately 60-80 K higher than actual filament temperature in some cases.

What I said, however, was that the relationship between CCT and filament _resistance_ was anybody's guess. The resistance of the filament is primarily determined by its thickness, in fact. The relationship between CCT and filament temperature is pretty well established, but does depend on a few additional factors, such as the fill gas, for example.

The relationship between CCT and efficiency IS known, however. The so-called "law threes" tells us that at 3330 K the efficiency of a halogen lamp will be 30 L/W, and that for each 100 K increase or decrease, that will change by 3 L/W, if we stay close to 3330 K.

And you keep mentioning that I said that at 6.8 volts Willie said that the filament was near its melting point. Could you please provide the link to that post, because I'm pretty sure that you're misquoting me.

But either way, what Willie actually said to me, was that the MN21 could safely be driven to 6.8 volts and that it was nice and white there, but that it could be pushed even more to 7.0 volts. However, at 7.0 volts it was pretty "smokin' " and was likely to have a very short life. And at 7.2 volts was right near the melting point.

For flashlights, you really can't go much higher than a CCT of 3400 or so because the filaments become to fragile as they approach their ultimate operating temperature. And this is completely setting aside the subject of soft-start and so on. So when I said that 6.8 volts was as high as you wanted to go (if that's what I said) I meant that it was the safest upper drive voltage, and not the point at which the filament would melt.

***

On another note, I never said you couldn't post here about whatever you wanted. I just ASKED if we could drop the whole ohmic question, but in the end said "suit yourself."

You think you are posting "for others"? I wonder what others would say to that?

You say I was "wrong" about end-to-end soldering? Yet you don't mention the fact that this was for the CPB 1650's only, and that it is my considered opinion that these cells have poor quality or insufficient seals. They leak and die all by themselves without any help from my soldering iron. Other AA and A cell packs I have soldered are all fine. All 100+ of them.

But let's get personal here at least one more time, shall we?

You don't really know me, Luna. You don't know that I was reading your posts in anger. Because, in fact, I wasn't. When I said I was sorry and let the whole thing go, I was no longer angry.

You question my maturity and ability to communicate like an adult. Fine. I don't know what's up with you, Luna, but something is. I wish you would go figure it out and come back with some positive energy and contributions, for your sake and everyone elses.

Honestly, I really shouldn't even be bothering to defend myself here. I believe that my credentials and accomplishments speak for themselves. Anyone can check out the links in my sigline and see this. Yet you are ever so quick to assume that I don't even know the difference between CCT and actual filament temperature. You have no respect for me, Luna.

Stop attacking me. Stop trying to make me angry. And stop trying to defend the notion that a filament's resistance is a constant over any significant range of voltage.


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## js (Feb 9, 2006)

Oh, and Luna,

Yes, I certainly WAS wrong about the reflector coating issue. I obviously admitted this when I asked if NewBie or someone else could say something authoratative regarding the coatings. I've been wrong about a great many things in my various posts here on CPF.

But that doesn't mean I am wrong about any one particular thing, or that when I qualify something and retract part of what I said earlier, that I am admitting to being wrong about the whole issue. I didn't need to ressurrect that thread on end-to-end soldering and mention the likely possibility that the soldering was causing the leaking USL pack failures, but I did. I did it because it was the right thing to do, because part of what I had said I now found needed qualification.

But for someone to then go ahead and grab that peice of good will and use it as a club to beat me with, . . .well, that's just not very friendly, is it?


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## js (Feb 9, 2006)

Everyone else,

If you have constructive (or otherwise) criticism and advice or comments or anything at all for me in regards to this interchange between myself and Luna, I am formally inviting you to send it my way via PM. I am aware that it is very hard if not impossible to get an objective and unbaised view of one's own actions in any given situation. If people of this community find me to tyrannical or offensive or aggressive and want to let me know about it so I can improve myself, I honestly want to hear about it. Let me know. I am willing to edit or delete any or all of my part of these interchanges with Luna if it will help matters.

I wish to be more positive and friendly and civil and helpful than I have been in the past. And in particular I'd like to apologize to AWR for my early posts about his LDO hotwire driver. They were out of line. As well as some other posts. I am sorry and I apologize and will do better in the future.

So, on that note, I'd like to bring up a topic for discussion:

The difference in relative transimission efficiencies of axial vs. transverse filaments in parabolic reflectors.

My immediate thoughts on the matter are that the axial radiates primarily perpendicular to the axis of the reflector, and thus will have less light that just goes directly out the front of the reflector. However, it will also not have light (or very little) that goes directly backwards towards the bore hole and potting material or bi-pin socket, or whatever.

So does anyone have any thoughts on this?


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## Luna (Feb 9, 2006)

*Quote JS*_
What I said, however, was that the relationship between CCT and filament resistance was anybody's guess. The resistance of the filament is primarily determined by its thickness, in fact. 
_

What? Have not heard of the transitive rule? If 
CCT->FilamentTemp
FilamentTemp->resistance

CCT-> ???
Guess what?


...
Oh yeah, you are pretty close "The resistance of the filament is primarily determined by its thickness, in fact" You just forgot the big variable in filament design, length

This is what we learned in first semester EE (or eng physics, its been a while): resistance = resistivity × length / area



*Quote JS*_
The relationship between CCT and filament temperature is pretty well established, does depend on a few additional factors, such as the fill gas, for example._

Where do you get that from? Gas fill alters resistance?

PS, on the CCT-> Temp. The 'around 300' comes from K->C conversion + variable . Pretty darn close.



Anyways, my ohmic approx matched brock's number not yours. So who is right? Don't confuse my ohmic approx with meaning constant though. I calced the resistance using know info an applied and used linear extrapolation to get the resitance at the other point. I said it is closely linear, not constant at hightemps. 
..cut..

bwaites[/b], He was wrong and Jar corrected him too on the reflector coating bit. 

Tell me one thing I was wrong about in this thread? 

You always come to JS defense why not address the technical and leave the personal out of it. I was called out I bit on the bait.

I think I have contributed quite a bit of information in this thread. Check out the links formulas. You have only done a little bit of backpatting and atttack my posts.


...
Inspite of the argument, this thread is generating a good deal of information for others. Once again, lets talk about this , not prior arguments. I will only address the technical issues from this point on in this thread. My statements all have been mentioned here before, I'm not backpeddling a bit


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## Luna (Feb 9, 2006)

JS, great start to productive discussion

_
The difference in relative transimission efficiencies of axial vs. transverse filaments in parabolic reflectors.

My immediate thoughts on the matter are that the axial radiates primarily perpendicular to the axis of the reflector, and thus will have less light that just goes directly out the front of the reflector. However, it will also not have light (or very little) that goes directly backwards towards the bore hole and potting material or bi-pin socket, or whatever.
_

My initial thought/guess woud be you are correct but the gains made could be offset by loss of light (uncolminated) due to more of the filament being up higher and outside of the optimal focal point. A deeper reflector would be necessary to reap the optimal benefits of an axial bulb


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## js (Feb 9, 2006)

Luna,

Yes. I was justing about to post that I misunderstood you when you said resistance was "linear" over a range, and was reading "constant". Yes. The filament resistance is approximately linear over the useful range of CCT's. Sorry about the misunderstanding.

Yes, I have heard of the transitive rule.

I agree with the CCT => Filament temp, but disagree with the filament temp => resistance. Not true.

As for filament resistance, yes, I did leave out length. I was typing in a hurry and forgot that part. I know how to figure resisitance from geometry and resistivity. The more important facts about filament geometry and optical/electrical characteristics are that the voltage of the filament is proportional to length and that the current is proportional to thickness, all other factors being equal. This is what I was thinking of when I mentioned length as an important parameter.

As for CCT and filament temp and fill gas, using a xenon fill gas will reduce the rate of vaporization of the filament. A reduced rate of vaporization can be used to increase lamp life, or increase filament temp. Thus fill gas can affect CCT.


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## bwaites (Feb 9, 2006)

Luna,

I will not rise to your bait and comment on personal attacks.

However, addressing only your points, if you actually had anything new and worthwhile to point out, I would be more than happy to congratulate you for it, however, nothing you have said here has forwarded the knowledge base at all. As you state, everything you have stated here you have stated elsewhere, fine. By your own admission, all you are doing is restating OLD arguments. BE done with it!

This thread was started as a comment on the success of subjective measurements and estimate vs. objective measurement of the output of lamps/lamp assemblies. 

That was it's intent and that is what the thread topic is.

If you cannot stay on that topic, (and nowhere does ohmic approximation enter into that topic, nor does anything else NEW that you have posted) please have the decency, as I asked before, to start your own thread.

I, for one, have just about decided that CPF is useless anymore, because every single serious discussion digresses into this kind of confrontation, every attempted good deed is punished. 

There always seems to be someone who wants to argue the most basic points, complain that they were mislead, and generally it seems to be someone who has not ever advanced a new idea on their own, never created a new light, never faced the real world problems associated with actually DOING something versus arguing and complaining about what others are doing. 

As one long time (and VERY respected) member pointed out last night in a private conversation, credibility is earned by DOING, and everyone on the board knows where the credibility belongs here. 

Bill


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## Luna (Feb 9, 2006)

bwaites said:


> Luna,
> nowhere does ohmic approximation enter into that topic, Bill



My friend, I didn't bring up the ohmic topic, I responded.


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## Luna (Feb 9, 2006)

*JS*_I agree with the CCT => Filament temp, but disagree with the filament temp => resistance. Not true._

See the link I provided here is a quote:

"Since the temperature coefficient of resistivity for pure tungsten is relatively constant over the range of lamp temperatures, it provides a convenient means for measuring the average temperature of a filament. "



here is the formula list

http://www.sylvaniaautocatalog.com/new_sylvania/imgs/voltage_var_equations.gif


As for the fill: Since temp is given it matters not if the environment is air, water, 100bar fill or oil. The fill just give longevity to to the specs, it cannot affect the resistance unless it is a conductive


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## Kiessling (Feb 9, 2006)

Gentlemen ... regardless of who started it, who is right and wrong ... PLEASE stop this non-productive war !
This thread is one of those treasure chests filled with info that can outlast the thread's active life by far, and I would *really* hate to see it die from bickering and mud slinging.
PLEASE ... calm down, step back, and reboot with "the art" in mind.
Thank you. 
bernhard

EDIT: non-compliance will have consequences.


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## js (Feb 9, 2006)

Luna,

There are some very subtle differences being thrown around here. Let's stop arguing and start trying to understand them, OK?

The CCT of the filament is the correlated color temperature. This is the temperature of a true black body whose radiation curve is closest to the radiation curve of the object under consideration. The fact that the CCT is HIGHER than the real temperature means that the tungsten filament is a BETTER radiator at higher temperatures than a theoretical black body radiator.

Now, filament temperature is not well defined, because the temperature of the filament is a function of the position along the filament, and the winding geometry of the filament. What do we mean by filament temperature? The temperature of the hottest point? The spatial average temperature? Or what?

I honestly don't know what is used for determining actual filament temperature or how in practice it is measured. These would be useful things to determine.

But in any case, if the temperature varies with position along the filament, and winding geometry, then does it not follow that the resistivity is also a function of position and winding geometry (number of coils, spacing, diameter of coils, shape of coils, etc.)? If so then wouldn't that also mean that the simple Physics 101 formula for determining total resistance would also become dependent on these factors?

I think this is so.

Finally, the fill gas has a role to play in these things as well. Take a look at page 7 of the "Tungsten Halogen Low Voltage Photo Optics" Osram publication. They say there that "The reduced rate of vaporization of the filament [due to using xenon fill gas instead of something else] can be used to . . . increase the luminous efficiency and color temperature by raising the temperature of the filament."

Raising the temperature of the tungsten and increasing its efficiency would mean more light for a given power. That much I can tell you. But how this relates to applied voltage and current draw, I can not say. Raising the temperature of a free bar of tunsten would necessarily increase its resistance. True. But as for a filament in a high pressure gas, I wouldn't know.

As for the ohmic approximation, you are well within your rights to bring it up and discuss it. I brought it up first. That's fine. But I have an honest, non-offensive, question for you:

Could you tell me why we would want or need to use an ohmic approximation that is linear with temperature? When would it come into play for us as modders, or how can it add to our understanding of incandescent lamps?

As for CCT, I didn't mean to say that one couldn't re-rate CCT based on knowing an applied voltage and a design voltage and design CCT at this voltage. What I said was that *you cannot accurately determine a lamps CCT from its voltage, current, lumens output, and life rating.* If only because the use or non-use of a xenon fill gas affects these things, and most probably other factors as well, such as mutual self heating of filament coils.

So, BTW, the re-rating formula for CCT which Luna is talking about is this:

CCT_applied=(Va/Vd)^0.42*CCT_design.

And it will re-rate a lamp with a known CCT. But it is useless if you don't already know the CCT.

Luna, perhaps I missed an earlier link that had a way to calculate CCT from other variables.


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## js (Feb 9, 2006)

Bernhard,

Right there with you. And I would ask that everyone else please focus on only the subject matter being discussed and disregard the perceived tone or intentions of the poster. Luna and I have agreed via PM's to do this. Wouldn't you all please join us in this endeavor.

Thank you for your cooperation, especially as it will prevent any chance of my thread being closed. I think it will end up having value even after the active discussion has ended.


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## Luna (Feb 9, 2006)

JS, I'm rushin out of the office right now but I will hit this right now: 

"Now, filament temperature is not well defined, because the temperature of the filament is a function of the position along the filament, and the winding geometry of the filament. What do we mean by filament temperature? The temperature of the hottest point? The spatial average temperature? Or what?"

In the PDF you posted, they have a good section on it (graph and table). They use average filament temp in K. Do remember to Kelvin to C translation


...

"Finally, the fill gas has a role to play in these things as well. Take a look at page 7 of the "Tungsten Halogen Low Voltage Photo Optics" Osram publication. They say there that "The reduced rate of vaporization of the filament [due to using xenon fill gas instead of something else] can be used to . . . increase the luminous efficiency and color temperature by raising the temperature of the filament."

That just simply means you can burn it hotter before the tungsten boils off, self collapses. There is no other magic involved. It doesn't affect the resistance of the filament. That is an attribute of material, not the environment.


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## js (Feb 9, 2006)

Luna,

As entertaining and fun as this may be for you, it isn't for me, and I would guess that it's not for anyone else who WAS following this thread (if they still are). I specifically edited this post to remove arguments I made because this thread is still not moving in the direction I would like, nor is it motivated by the spirit it should be.

So how about this, you win, alright?

Filament temp and CCT are both uniquely and completely determined by a certain definition of average resistance and/or resistivity of the filament.

Let's agree that you are right about this. So,

1. Please link to or post the formula for R vs. CCT.

and

2. Tell us all why we as CPFers and/or modders and incan afficionados can find this to be useful.

For example, consider a high voltage, low current lamp. The resistance of the filament by definition is V/I, of course, but what is the CCT? How does CCT relate to other parameters of this lamp? The filament would be long and thin, yes? How long? How thin?

Next consider the WA 1160, a low voltage, high current lamp, and answer the same questions, if you would.

Take us all on a journey! I would love to know more about lamp design. Tell us how you would design a lamp. What steps you would take, at least from a theoretical point of view.

And if you could discuss the Osram 62138 vs. the 64440 IRC, both 12 volt lamps, one 25 hrs of life, the other 4,000 hours. One filament short and thick, the other much, much longer and thinner, then that would be great as well. And an explanation of how the IRC coating improves efficiency would be appreciated.

I had planned on talking about some of these things myself at some point in this thread or somewhere else, but I figure that instead of us arguing about things, I will just let you lead the discussion since you seem to me to be quite sure of your knowledge and competence.

I'm not being ironic here. I want you to clarify and explain all of these things. I no longer want to hear about how I am wrong. Rather I want to hear all about how you are right.

Seriously. I can host pics for you if need be.


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## tvodrd (Feb 9, 2006)

Jim,

If my short post offended you, I apologise. I remembered some very informative posts Jar had made wrt reflector efficiency. It was a real good start to the missing 35% out the window. The post was meant to encourage him to chime in.

Larry


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## andrewwynn (Feb 9, 2006)

My 2 cents.. 

Hey.. if there was a useful way to use filament resistance and have a formula that is helpful, i'll chip in $5 of that $20.. If it's shorter, easer, faster or more accurate, awesome. 

I'm not kidding either. I have had the formulas be way off recently and would like to figure out why. (with my Mag100.. the current re-rates to 8.78 when driven to 13.2V (only 16% overdrive).. however with a measured bulb voltage of 13.2, i have consistently measured over 9A going through the circuit, and would like to know why. 

Other than that one example, the re-ratings have been dead-on, almost to a scary level.. http://hotrater.rouse.com has the spreadsheet that will calculate all the values including CCT of a bunch of WA lamps, and you can add your own just by copying the right rows and filling in the blanks. The best part of that spreadsheet is that it actually is the first case of which i'm aware that takes into account the resistance of the host and automatically 'goal seeks' to find the equilibrium voltage and current. (i.e.. you put in a higher Vbat.. it will put in a higher current but than that means more of a voltage drop on the switch.. it just 'figures it out'). You will notice that the spreadsheet includes both Bulb and Torch lumens and it naturally uses the 65% factor, but it would be a cake-walk to change it to 70% if you wanted to estimate a little higher, maybe with an MR16 lamp and no lens for example. 

The formulas used in that spreadsheet do wonders for estimating Vbat and Vbulb.. current, CCT, and i put i some neat 'extras' in there like a 'distance to melting'.. yes i'm aware that CCT is not really the K temp of the W, but it's a very useful figure for comparing lamps, since the CCT numbers are very hard to keep track of.. 10% 'from melting' is where lamps really start to look nice.. 5%.. they are brilliantly white.. and -3%.. well thats where you for example accidentally short out a wire and put Vbat of 8.3V on an 1160 lamp.. wow did that look cool.. maybe not worth the $9 it cost me, but very cool. 

Hey, btw JS.. not an iota of hard feelings about the tough love on the hotdriver post, which we settled long ago, or the minor oops referencing my comment about 3000L light when i actually did mean torch lumens.. As it turns out, my Mag100 as well as the USL are closer to 2500 with the lamp they are using but i have some of the transverse filament lamps on order that will bump it up OVER 3000L, so i left the title, and even the first post was edited to make it clear there was initially a goof in my formula (i had the initial bulb lumens off by 600). 

So far in my testing i've been very happy with sticking with the 65%, and thank the people that went through the effort of giving us a baseline, even if it is not 'perfect'. 

I'm interested in knowing more about using bigger or smaller reflectors and the effect on this factor and more so i am interested in why.. when i would estimate a mere 440BL from my RT4, does it ceiling bounce a number that puts it really near to 400TL? (not that i'm exactly complaining.. that is a veeeerrrryy bright LED light monster). 

Back to Luna.. hey please start a thread about the filament R so we can chat about it over there and not on this thread.. i am interested in seeing if i can figure out a more accurate way to estimate current v voltage with the osram 100W lamp.. the formulas from the WA are not cutting it. (sorry if that opens a can of worms.. please open that can on said other thread though). 

Back to JS.. and back on topic.. thanks again for going through the effort of taking an IS to the lamp and get a more accurate measurement of Bulb v Torch lumen and verify what we've been using to be so useful. 

Any chance you could do a test with some LED high-power lights? i could work out a short term loan of the RT4 and we can reverse-engineer what the output is supposed to be for the Ubin emitters i'm running to get a reflected value.. or even possibly I could make up a jig that would enable putting a McR20 reflector onto a controlled output high-output lux.. with a very large copper heatsink that effectively will keep the slug at room temp for a few minutes or something? 

-awr


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## js (Feb 9, 2006)

tvodrd,

Not at all. Not at all. I was being speaking tongue in cheek, or whatever that expression is. I always love it when you post to my threads. It's really great to have you around, Larry.

AWR,

You are a very generous and well intentioned person, Andrew. Thank you. BTW, sorry you were sick recently. I hope you are feeling better.

As for the post I made above about the formula for R vs. CCT, I realized that I was only going to perpetuate a discussion I wanted to end. So I changed the post and deleted my offer of $20, because I'd just have to spend time discussing the formula and inevitably, arguing about it. I don't want to do that anymore. It's not fun and it's not productive, and I've been preoccupied with this whole thread all evening and it got in the way of my work efficiency. I got less done. And I NEED to get a lot of stuff done. M6-R orders for starters. I'm sure you can relate with the whole nanos project. Plus all the other four or five irons you've got going in the fire, Andrew. You are an impressive whirlwind of activity.

Anyway, as for an IS test of the RT4, it's a great idea, but at this point, I'd rather have someone else pick up the ball. I can give you the contact info for LSI in Arizona if you want, but there are plenty of other labs that do this sort of thing. Why don't you organize it, Andrew? Start another thread on it! Get contributions from a bunch of people. Publish the results. I'll chip in for sure!


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## Luna (Feb 9, 2006)

Js, you still think I trying to prove you wrong. I was just answering your doubt with a link you posted. I'm sorry, I was just replying quickly in an effort to stimulate discussion as I mentioned in the PM. Please dont be offended, this is all a tech discussion. Nothing more.

AWR, I'll try to assemble a new thread to show how the rerating formulas are derived ASAP. You can follow the other thread where I uses temp/resistance to derive the current or an MN21 and use the same work flow in the meantime. I don't have a problem with the rerating though. My method was just a stopgap in the abscence of the data I needed.


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## NewBie (Feb 10, 2006)

Okay, I spent the night running simulations (the past 5 hours).

In the setup, I had the rear hole, the bulb base, reflector, AR lens.

Generally, as the reflector focal length got really short, which places the filament towards the rear of the reflector (rear hole end, not front), the non-usable area increases in relation to the other usable area, and I saw losses up to 30% of the output, for normal reflectors (not cut-off bananna uber short focal length looking deals). Inversely, as I moved to a longer focal length, the losses dropped considerably, as well as when I made the bulb diameter more narrow.

The bulb base shadows the hole. Draw lines from the filament to the bulb base, and keep them going to the reflector surface. You will see there is a shadow area, so it would not matter if you had a larger hole in the reflector than the bulb diameter. But it starts hurting you, once you grow the hole larger than the shadow. PR type bulbs have quite large shadow areas, as well as a large internal base.

This shadow area is also related to the focal length of the reflector, and how far the bulb is inserted into this reflector.

With the Alcoa Everbrite 88 finish (88% reflectivity), which is a special processed metal mirror material, the losses due to the reflector surface finish, in relation to the light out the front resulted in a contribution of 13.33 %, of the total beam output losses.

Using a perfect 100% reflective reflector surface, the flashlight output rose by 12.24%. Enhanced protected silver reflector coatings approach this 100% level, and there is some variation from manufacturer to manufacturer.

When using the Alcoa Everbrite 92% coating instead of their 88%, the beam output increased by 5.08%. (yes, I do know that there is only a 4% difference...)

Using a ultraclear borofloat lens (colorless when looked edge on), and a Magnesium Fluoride AR coating, the losses I see due to the lens in simulation are 3.14%.

Using a ultraclear borofloat lens with no AR coating resulted in losses of 8.17%


------Numbers below this line are not based on simulations.

Unfortunately, I didn't have water clear in the database, nor did I have float glass (soda lime). Lower end borofloat glass types and low iron soda lime glasses will look yellowish, edge on. Losses would have been higher with either of these options.

In one of my way back posts here on cpf, I did talk about the difference in loss when using standard green hued soda lime float glass (green when looked at edge on), with more details. With just standard sodalime float glass and no AR coating, the typical number worked out to 11% loss. There was an earlier post where I talked a bit more about the losses based on thickness, but I don't have the numbers offhand.


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## Luna (Feb 10, 2006)

> When using the Alcoa Everbrite 92% coating instead of their 88%, the beam output increased by 5.08%. (yes, I do know that there is only a 4% difference...)



Makes perfect sense because not all light exits the aperature in a single reflection. 


Good job!


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## NewBie (Feb 10, 2006)

Luna said:


> Makes perfect sense because not all light exits the aperature in a single reflection.
> 
> 
> Good job!




No kidding. Thats what I was explaining to folks when we talked about the losses a few years ago. Went thru and calculated the losses of a single ray, and how it progresses, and the reflection, and the return, and the re-reflection, same thing even happens in the glass lens.

Wish I could find that post, but I can't find it anywhere.

Now, if we could just find a low-cost source for decent reflector coatings...


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## Luna (Feb 10, 2006)

If it isn't too much trouble please do the raytrace for a wider reflector (same depth) and I'd bet the internal reflection reduces. This is the basis of my position of the wider reflector being a little bit more eff. 

_
Now a reflector with the same depth will have a lesser amount of incident losses because less light will reflect back to the source or rereflect back to the reflector due to the changed geometry.
_


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## Luna (Feb 10, 2006)

ADD: (sorry using notepad to compose messages)



> Now, if we could just find a low-cost source for decent reflector coatings...



I learned true chemical mirror silvering in my youth in an effort to build telescopes and do holography. Maybe it is time to relearn it. That just leaves the need for protection. I wonder how good the antiscratch/AR coatings are optically that these 1hr eyeglass makers use.


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## js (Feb 10, 2006)

NewBie,

Excellent post. Thanks so much for going to all the trouble.

So, the double, triple, or even higher multiple reflections are obviously something that have a role to play. I really wonder what kind of effect a heavy orange peel or even stippled reflector would have on transmission losses. Obviously, it would negative impact the percentage out the front of the light, but by how much? Good thing for AWR to add to include in his IS tests, I would say.


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## Icebreak (Feb 10, 2006)

I accepted 65% loss due to my blissful ignorance and ridiculous way of thinking about things.

Take the lowly chicken egg. Empty it then reflectorize the interior with virtually 100% efficient reflective material. Virtually model a source of light and float it inside the egg.

There will be two sweet spots in the egg at each end that will reflect the rays axially in either direction. The perfect photon management system. Except you won't have a beam.

Darn. I guess we will have to chop a third of it off to let the light out. Hmmm 1/3. OK 33.33 from 100 is 66.67. Then subtract a little for the heck of it and you get your 65% efficiency.

Here is a regulated metal egg:







Here are a couple of nice egg reflectors:











So what happened to that perfect ray management system? Dang. 35% chopped right off leaving you with 65%. If only we could just keep the shape intact but have a reflective medium that was also invisible.







Enter TIR. I've thought that it would work for some time now and I guess Luna thinks it has possibilities. How about this one? Focusable. Yeah.






The chicken came before the egg. The egg came before the parabolic reflector. Incandescent TIR optics for flashlights are next. Since I don't profess to be an expert of any flashlight technology I won't debate my point but I would like to hear others' comments.

Except the chicken and the egg part. I KNOW the chicken came first.

- Jeff


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## andrewwynn (Feb 10, 2006)

That is really funny.

Technically the chicken probably had some eggs inside, so they maybe came at the same time :-D


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## offroadcmpr (Feb 10, 2006)

Sorry if this has been said before, I don't quite understand everything that is said here.

What causes the loss of light? the Lens only takes away a few percent, so is it the reflector? What else causes the loss of light?


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## KevinL (Feb 11, 2006)

andrewwynn said:


> That is really funny.
> 
> Technically the chicken probably had some eggs inside, so they maybe came at the same time :-D



No, the rooster came first, that is why the hen was not really happy about how the evening turned out.


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## NewBie (Feb 11, 2006)

Luna said:


> If it isn't too much trouble please do the raytrace for a wider reflector (same depth) and I'd bet the internal reflection reduces. This is the basis of my position of the wider reflector being a little bit more eff.
> 
> _
> Now a reflector with the same depth will have a lesser amount of incident losses because less light will reflect back to the source or rereflect back to the reflector due to the changed geometry.
> _




Well, spent several more hours modeling and simulating. 

Since less light hits the reflector surface, there is less light that is absorbed by the reflector. So, techically, you get more lumens out the front of the light, but you get a much less intense beamspot (basically the flood area is larger).

Rarely are things a free lunch.

As far as the light rays, when they bounce off the reflector surface, they are going parallel to the beam, and lets say the back reflection source is the glass, it bounces back, and travels right back to the filament, the same thing with a narrow diameter reflector with the same length.

However, there is a tremendously higher loss of light to the flood area, as much less of the light hits the reflector.

With the larger diameter(3" vs. 2"), same length reflector, the hot spot is larger with the larger reflector.

Since the hotspot is larger, due to the larger reflector, the peak brightness ends up lower. How much? 39.9 % lower peak brightness (hotspot is dimmer but larger).

FYI, I modeled an actual filament, not a point source.

Since the filament is not a zero sized spot in space, with the longer focal length reflectors, the light rays are "focused" more accurately. Even when the filament is centered, and the center of the filament is centered at the focal point, the end of the filament is not at the center. Since the focal length is longer, this "off-center" end of the filament has less of an angular error contribution.

Thus, the longer focal length reflector results in a larger, more dim hotspot, but the edge of the hotspot is much more defined. Where the narrower diameter, shorter focal length reflector has more angular error, and ends up looking more like a hot fuzzball that fades at it's edges. The narrow diameter reflector (short focal length) is quite a bit brighter at it's hottest spot.

Though, you don't want to keep shrinking the reflector diameter, as you get to a point at which the angular error increases, and the ball grows in size. If you could shrink the filament size at the same time, at least you could maintain what you had.

Now, if you continue to grow the longer focal length reflector, in the depth or "length", until you reach the same maximum exit angle of the flood as you would with the shorter focal length smaller diameter, then you end up with the same sized flood area, with more of the beam directed into the hotspot. The hotspot increases in diameter, but the peak intensity does not change.

Anyhow, I hope folks found this stuff interesting, as it sure took an awful lot of time to do.


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## andrewwynn (Feb 11, 2006)

that actually is fascinating.. did you do anything with LED vs filament.. i'm very intrigued by the 360 deg. output of a filament vs 180 of an LED to see how that affects the 65% number.. since apparently i'm getting a lot more than the 65% i'd have expected from my BAM! 

I should be getting less than 300TL out of BAM if the 65 figure plays.. i doubt i'm getting much more than 120BL from the 4 emitters.. they are Ubin emitters overdriven 10%.. so i doubt more than 120BL each (should be about 100-110L at 1A)... in any event.. when i do bounce tests with lights of a known TL.. ala M6 or a Mag85.. the estimates come in closer to 380-400TL.. quite a sight to see for LED btw.. anyhow.. i would love to see a test like i mentioned earlier.. maybe when i get done with making nanos i can play with that. 

-awr


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## NewBie (Feb 11, 2006)

andrewwynn said:


> that actually is fascinating.. did you do anything with LED vs filament.. i'm very intrigued by the 360 deg. output of a filament vs 180 of an LED to see how that affects the 65% number.. since apparently i'm getting a lot more than the 65% i'd have expected from my BAM!
> 
> I should be getting less than 300TL out of BAM if the 65 figure plays.. i doubt i'm getting much more than 120BL from the 4 emitters.. they are Ubin emitters overdriven 10%.. so i doubt more than 120BL each (should be about 100-110L at 1A)... in any event.. when i do bounce tests with lights of a known TL.. ala M6 or a Mag85.. the estimates come in closer to 380-400TL.. quite a sight to see for LED btw.. anyhow.. i would love to see a test like i mentioned earlier.. maybe when i get done with making nanos i can play with that.
> 
> -awr




Are you accounting for die heating, and slug heating above ambient Andrew, and derating for that? The temperature of the slug is easy to measure, and then you know your watts going into the die, so with the C/W specified in LEDs, you can then derate the lumen output rather accurately. Especially when comparing with their 25C die temperature binning. Unfortunately, this ends up being an awful lot of loss in the real world.

Yes the situation is different with LEDs. How, I'll let you go spend 15,000.00 for the software to find out, and the time learning to run it, then working out a model that reflects reality, and then run the simulations in various configurations. Though, for the very basic situation in flashlights, it is alot cheaper, and efficient, to go do integrating sphere tests in the real world.

I will tell you that in the LED scenario, the AR glass, using a much higher grade substrate than found on most AR lenses here on CPF, which is water clear looking edge on (no tint), and a very high grade AR coating, the loss works out to 3.1-2.68% in simulation, depending on the scenario.

Also, as far as the hotspot area (not including flood area), on a "perfectly machined" reflector, and a pretty decent grade coating, with an 85% reflectance, plus the high grade AR lens, versus a 100% perfect reflector w/o a lens, the impact is 17.6% loss.

The losses are less in the flood area, since this is light doesn't hit the reflector surface and suffer the losses.

My simulation for the LEDs scenario mentioned above does not include the losses for the acrylic dome or the silicone gel fill on the return path, nor the losses for the light hitting the phosphor on the return path from the AR lens. So, in reality, the losses would go up a little- LumiLEDs does not give us numbers for those properties.

Too bad we can't get decent grade reflector coatings with a protective overcoat, instead of these very lossy flash aluminum coating (or vacuum metalized) which degrades very rapidly on exposure to air- at a decent price. That and those really poor Rhodium (~75%) and Nickel (55%-when bright or enhanced) coated reflectors which are even worse...

One thing that does irk me, is that some reflector manufacturers will specify a 93% reflectance for their Aluminum coating, but this is only if it is always kept in an inert atomsphere. The reflectance can quickly drop to 65-80% when exposed to air and time.

It is too bad that IMS does not offer their reflectors with a decent coating at a higher price. Yes, the IMS reflector coating has a rather low reflectance number, and high losses.

Reflector coatings, pass your pointer over the coating on the side:
http://www.optiforms.com/4000services/4100opticalCOATINGS/41401ocREFLECTIVITYmetal.html

Found another interesting reference for reflector coatings:
http://www.vergason.com/PDFdocs/Performance_Coatings.pdf

A reference for one brand of reflector coatings:
http://www.mellesgriot.com/products/optics/oc_5_1.htm

Another:
http://www.lambda.cc/PAGE69.htm


For the techical folks out there, Melles Griot has alot of interesting subjects to look at (notice the next button on the bottom of the page):
http://www.mellesgriot.com/products/optics/oc_5_1.htm


A cool AR lens coating comparision (run pointer over the coating at the side):
http://www.optiforms.com/4000services/4100opticalCOATINGS/41403ocREFLECTIVITYar.html


A reference for Bright Nickel coatings, placing it at 55% reflectance:
http://www.shd.org.yu/HtDocs/SHD/Vol67/No6/V67-No6-07.pdf



.


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## Icebreak (Feb 13, 2006)

Newbie -

As always your hard work is appreciated. I've mentioned before that your reports, though technical, are easy to read and with some effort, easy to understand.

I wanted to ask what your opinion of the premise of my egg shell analogy is. That is it should be no great shock that a good reflector can only be about 2/3 efficient because a light source cannot be 100% managed by a reflector because the beam has to be released through a window and that window area won't be able to be used for ray management.

I picked on the chicken egg because it has two parabolic vessels in opposition making a complete container.

Though almost caveman-like in scientific view, it makes sense to me.

Another simplistic way to look at it is if a lamp is engaged with an Integrating Sphere and measures 1000 lumens then 35% of the IS is sawed off (and the rest of the device's measuring ability is not compromised) it would be no surprise if the lamp then registered 650 lumens or 65%.

With no concern for good geometery, source to surface ratio, focal point or reflective material quality; I don't think that even an almost perfect reflector could attain better than 70% efficiency.

Further, I think an optic using internal reflection has possibilities. If there was a structure in the optic above the source that also used internal reflection to bounce back the rays (that would normally be released unmanaged out the front) back to the primary reflection surface (not uncommon in incandescent lamps [or think carbon arc]) it may be possible to attain higher efficiency than a reflector can offer.

It is not unlikely that I have completely missed what you guys are talking about.


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## NewBie (Feb 13, 2006)

Icebreak said:


> Newbie -
> 
> As always your hard work is appreciated. I've mentioned before that your reports, though technical, are easy to read and with some effort, easy to understand.
> 
> ...




In a number of lights, you'd melt a plastic optic, and glass optics are spendy. That, and every optic I've seen so far uses cheap acrylic/polycarbonate, which themselves absorb alot of light. By optics, an example would be the NX-05, Fraen, or POL.

Another approach would be lenses and reflectors.

That said, there are some compound reflectors that will gather the flood part of the beam.

For things reflected off the reflector surface, a Protected Enhanced Silver coating would get you over 98% reflectivity.


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## Icebreak (Feb 14, 2006)

Thanks for the response, Jar.

The optic would have to be Pyrex or something similar.

It looks like it's possible I didn't understand what you guys were talking about. Surface reflective efficiency and bulb lumen to torch lumen differential efficiency, of course, are two different things.

If it were the later (like the thread title) I think my egg shell theory shows an obvious answer.

I see it like this: Chop off 35 to 30% of a fully contained photon management system and correspondingly ~60 to 65% will project out the torch.


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## cy (Feb 15, 2006)

JS, newbie, great info!!!!


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## andrewwynn (Feb 15, 2006)

This reminds me of an interesting idea i've had.... i want to take the likes of a luxeon and mount it the the focus of a satellite dish.. and treat the dish to be a mirror.. either by the likes of chrome and possibly silver plating.. or in the reverse of a minitature 'death ray'.. using the likes of 1cm square mirrors and gluing them on to the parabola. would *this* soultion get me higher than the 65.. theoretically if the beam from the emitter wasn't wider than the dish it would collect all the light and only the reflective % comes into play. I'm still very curious about the difference of emitters vs filaments and my practical measurements that seem to indicate a number far higher than 65% comes into play.. maybe having somethig to do with incident angles and what % of the light is lost from the base shadow in a lamp where in an emitter, the light only comes out the front to start with so there is no 'shadow' factored in.. though.. technically i suppose the reality is that upwards of HALF of the light is being shadowed.. i'm sure that the light emitting die emits light out the bottom into the glue or whatever is holding it do the heat sink.. which mostly is absorbed... hmm. we need to develop an LED that floats on a transparent aluminum heatsink so we can harvest those photons as well. (seriously some fairly heat-conductive glass i suspect could be used.. imagine putting an LED die in a vertical arrangement held up as if it were a filament.. and letting the light out from both sides of the 2-dimensional array.. it could be held in a relatively thin copper or silver frame that would mask extremely little light, less than the filament wires of a normal light bulb.. hmm.. that sounds like a very interesting experiement. 

-awr


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## bwaites (Feb 15, 2006)

Andrew,

Isn't the satellite dish idea essentially what Pelican did with it's "Recoil" line of flashlights, (M8 LED, etc.). They have VERY tight beams and almost NO spill.

Bill


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## andrewwynn (Feb 15, 2006)

i believe so.. i've never seen that light but i started a thread a long while back talking about inward facing emitters.. the dish idea is taking that to extreme with a much bigger reflector.. aiming for a zero degree beam focus.. a cylinder of light ala maxabeam, but using the likes of a K2 emitter at 1.5A or something.. the neat thing about the sat. dish is with the offset boom it has no shadow at all. I don't know what the practical use of such a device is i just have an interest to see the maximum focus of the likes of a single emitter solution.. how far can a beam be shot. I think i might pick up a used dish just for fun this summer.. to make a 'mini death ray' that can be used in reverse to shine a lux spot as far as possible. 

-awr


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## bwaites (Feb 15, 2006)

The recoil beam is square, the only square REFLECTED beam I know of, so the angle of reflection is close.

Bill


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## andrewwynn (Feb 15, 2006)

wow.. i guess the beam would be square if it's a good enough aim.. neat (and somewhat annoying) but it would have to be of course. guess i'm looking foward to a square beam :-D

-awr


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## NewBie (Mar 3, 2006)

cy said:


> JS, newbie, great info!!!!



You are very welcome CY!


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## brightnorm (Mar 6, 2006)

bwaites said:


> ...As one long time (and VERY respected) member pointed out last night in a private conversation, credibility is earned by *DOING*, and everyone on the board knows where the credibility belongs here. Bill


That sure sums it up for me

Brightnorm


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## Luna (Mar 6, 2006)

brightnorm said:


> That sure sums it up for me
> 
> Brightnorm


 
Very insightful addition there to such a pleasant month old thread !


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## NewBie (Oct 8, 2006)

Folks in chat were asking about Rhodium reflector coatings, and some very useful info is in this thread, regarding that subject.


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## mpteach (Oct 21, 2006)

If I can sum this up, untill we get access to quality reflector coatings and AR lenses that are durable enough to actually use, 35% of the light generated in our incandescent lights wont leave them. When we do get the good stuff 15-20% more of the light will get out.


I have a question too. How much output can be lost to fingerpnrints on the the outer side of the lens ? AR coated and regular lenses.


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## tebore (Oct 21, 2006)

mpteach said:


> If I can sum this up, untill we get access to quality reflector coatings and AR lenses that are durable enough to actually use, 35% of the light generated in our incandescent lights wont leave them. When we do get the good stuff 15-20% more of the light will get out.
> 
> 
> I have a question too. How much output can be lost to fingerpnrints on the the outer side of the lens ? AR coated and regular lenses.


 
If it's bad enough it can be like 10%-30%. Like using a stock mag lens "blocks" ~5% more light than a UCL. In some cases in old mags you can notice a huge difference when you replace the old lens with a new plastic one from mag, because fine hairline scratches can claim quite a bit.


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## NewBie (Oct 22, 2006)

mpteach said:


> If I can sum this up, untill we get access to quality reflector coatings and AR lenses that are durable enough to actually use, 35% of the light generated in our incandescent lights wont leave them. When we do get the good stuff 15-20% more of the light will get out.
> 
> 
> I have a question too. How much output can be lost to fingerpnrints on the the outer side of the lens ? AR coated and regular lenses.




I've yet to see any flashlight lens provider offer it, but there is a coating that can be put on the AR that is oleophobic and hydrophobic, which doesn't fingerprint or smudge, nearly repels dust, anti-static and makes the lens very easy to clean. It has been a number of years since it has been available, and it is only a matter of time before someone offers it.


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## mpteach (Oct 22, 2006)

NewBie said:


> I've yet to see any flashlight lens provider offer it, but there is a coating that can be put on the AR that is oleophobic and hydrophobic, which doesn't fingerprint or smudge, nearly repels dust, anti-static and makes the lens very easy to clean. It has been a number of years since it has been available, and it is only a matter of time before someone offers it.




Is that similar to this http://www.schneiderkreuznach.com/knowhow/mrc_e.htm

Theyre not cheap. http://www.bhphotovideo.com/bnh/con...ls&Q=&sku=11989&is=REG&addedTroughType=search


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## NewBie (Oct 22, 2006)

Actually, if you buy in batches, you can get the additional coating for nearly nothing in comparison to the cost of the normal AR lens.


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## mpteach (Oct 22, 2006)

Besides the expensive 52mm photography filters, I have seen 2" and 50mm AR windows which are reasonably priced, will these fit a D mag??


Some people will spend rediculous amounts of money to get the highest performance materials, but AR coatings are actually economical at higher power levels. For instance im buidling a mag 2d w/ an overdriven 50w or 65w IRC bulb.

At 3700L an 8% increase in output is roughly 300L. I wouldnt mind spending $20 for a durable and AR coated lens instead of $5 on a simple borrofloat one. And even more so for a good reflector.

How long does it take for an unprrotected aluminum reflector to heavily oxidize?

Edit: What % loss is there using a stippled reflector?


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## cy (Oct 22, 2006)

has anyone tried a glass treatment?


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## bwaites (Oct 22, 2006)

Most of the AR coatings won't stand up to the heat from the 100 watt lamps, and the windows are not Borofloat so they will shatter!

Ask me how I know!

There were some heat treated UCL's made, and I did have one of those last a few months in a USL before if finally gave up the ghost and shattered one day.

Bill


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## NewBie (Oct 22, 2006)

bwaites said:


> Most of the AR coatings won't stand up to the heat from the 100 watt lamps, and the windows are not Borofloat so they will shatter!
> 
> Ask me how I know!
> 
> ...




Oh, you mean in close proximity. The Thor 10MCP and 15MCP use nothing more than ordinary window glass (soda lime float) and even that does not shatter.

If I recall correctly, UCL is simply low iron soda lime (aka crown glass), where the glass itself has a little bit less transmission loss, and thus the glass tint shifts from green to brown to yellow, to water white when looked at edge on, as the amount of iron impurities is reduced.

And B270 is a high quality optical grade of Pyrex, which is what those lab beakers you do chemistry experiments over flames, are. B270 is actually a borosilicate glass. Other names for borosilicate glasses are, Pyrex ™ by Corning and Duran ™ or Borofloat ™ by Schott Glass. When heated, it's expansion rate is 3 times less than soda lime glass. Borosilicate glass is mechanically stronger and harder than soda lime glass.

Quartz is higher up on the list, it's thermal shock resistance is even better which has a coefficient of expansion ~60x less than even the borosilicates. It has a continuous maximum working range of 900C to 1100C, depending on the size and shape of the part. It can be used up to 1400C for short periods of time. 

Not all AR coatings are created equal, nor are they deposited equally.


AR coatings can be put on window glass, UCL, B270, quartz, sapphire, mineral glass, quartz, and more.


There are two typical ways of depositing AR coatings, one is vacuum and the other is sputtering. Usually, the vacuum deposited coating is more durable and higher quality, but it is slightly more expensive. One of the processes I've seen, heats the AR coating material above 2,227 °C in the process, to turn it into vapor, and it condenses on the glass.

As far as shattering, consider how many folks will mount the lens in a Maglite, and the edges of the glass are cooled by the metal housing, while the center is heated. Thats a shatter scenario.

Even sapphire and mineral glass can be thermally shocked and broken if not heated uniformly. 

Magnesium fluoride itself (which is what most AR coatings are made from) is a proven window material for power Eximer lasers, but over time, it will color a bit, even under this high power assault.

Bwaites-

I believe your issue is not the AR coating, but the lens substrate, and un-even heating of the substrate. Some substrates (the glass), are more prone to shattering due to high stress levels, caused by uneven heating.


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## mpteach (Oct 22, 2006)

Do you know where to get ar coated b270 lenses that fit mags?

Isnt quartz sensitive to fingerprints though? I know that im not supposed to tuch 500w halogen work light bubls directly.

I broke a pyrex measuring cup heating water on a stove burner. However i have pots that are a really yellowish brown glass that are made for that and fine. What kind of glass are they?


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## js (Nov 18, 2006)

I'm getting together a thread on Lamp Physics that I hope to post sometime soon, as it's all been sort of obsessing me lately--ever since the 60 l/watt thread on the Osram IRC lamps and this post that I made to it.

Backing up, for starters, Luna was right. IF you know the CCT of a lamp filament, THEN you know its Temperature, and IF you know its geometry, it's pretty straightforward to come up with the total resistance of the filament at that temperature, or I should say, at that _average_ temperature, with the average being defined in some reasonable way.

Also, Luna was right, for the most part, in saying that using xenon as the fill gas allows for greater efficiency by allowing for a hotter filament that nonetheless has the same rate of vaporization as a cooler filament in a nitrogen/argon fill gas.

Good for you Luna!

That said, I will bring back a quote of my own from earlier in this thread:



> As for CCT, I didn't mean to say that one couldn't re-rate CCT based on knowing an applied voltage and a design voltage and design CCT at this voltage. What I said was that *you cannot accurately determine a lamps CCT from its voltage, current, lumens output, and life rating.*



And that was at the heart of my unfortunate argument with Luna. And I stand by that. And the whole IRC issue brought everything to greater clarity for me regarding this.

Because, the electrical current used to power our lamps is only a means to keep the filament glowing hot. It's the hot tungsten that radiates the light, because IT IS HOT, and not because current is flowing through it.

Next, the real issue is that what we directly control is not the filament temperature, but rather the applied voltage (or current in some unusual cases). A voltage is applied, current flows, the filament heats up until it reaches a steady state situation where the power applied to the filament equals the heat lost due to radiative cooling of the tungsten filament blackbody radiation and convective cooling due to the moving fill gases within the envelope. The temperature and motion of the air outside of the bulb envelope, as well as any radiation incident upon the filament itself (such as from a nearby reflector), affect the rate of heat-loss, and thus the temperature of the filament. But change the filament T and you change its R and you thus change the current. In all of its messy glory it is VERY complicated--and I mean from a theoretical perspective, including the convective gas flow currents within the envelope and just outside of it, as well as the blackbody radiation formulas and rate of vaporization formulas and so on.

However, some qualitative things can easily be ascertained. For one, if you reflect the radiation, or any part of it, back towards the filament (the blackbody), then it will increase in temperature FOR THE SAME APPLIED VOLTAGE, and thus the current drawn will DECREASE, and thus the power will decrease. Now, if the visible light is allowed to pass through the reflective layer, then the lumens output will INCREASE at the same time that the POWER will decrease. This is the idea behind the IRC coating. In principle, it's as simple as insulating your house. The same woodstove burning at the same rate will now keep your house much warmer than before it was insulated. OR, you can keep the same temperature with a REDUCED amount of wood burning. Insulation. That is, in essence what the IRC coating achieves.

So, anyway, I was going through my physics books, reviewing the blackbody curve and total radiative power of a blackbody of area A and emissivity e at temperature T (in Kelvin, of course), and I decided it would be fun to apply it to a known lamp, such as the Welch Allyn 01111-u.

Great idea, I said to myself. It is a 6.0 v, 3.35 A, 20.1 W, 465 lumen lamp running at a CCT of 3,325 K, with a life rating of 100 hours. A quick division shows it to have a 23 lumen/watt efficiency.

Now, that struck me as low for a filament running that hot. According to what I've read, a 3,300 K filament should have about a 30 l/w efficiency. Hmmmm. What was going on?

Then I remembered a conversation I had with David Harchenko of Carley Lamps. I was spec'ing a lamp and getting a quote on it, and we were talking about CCT and I mentioned a Welch Allyn lamp, and David immediately stated that WA always arrived at significantly higher CCT's than Carley did. He said he thought that they focused right in on the center coil of the filament for their measurement, whereas Carley had a different procedure that gave a much more realistic assesment of the true blackbody equivalent temperature.

Interesting, is it not? At the very least, it implies that there is no standard way to define or measure the CCT of a filament.

So, that got me curious. So I looked up some Carley lamps, and examined the Carley 852. It is also a Halogen lamp, with a xenon fill, and it is also a 6 volt, approximately 20 watt lamp, so it would make for an interesting comparison:

6 volts, 3.3 amps, 19.8 watts, 40 MSCP = 500 lumens, driven at 3100 K, with a 20 hour life. These figures yield an efficiency of 25 lumens/watt. Now, if at 3300 you have 30, and if for every 100 K difference you add or subtract 3 l/w, then this lamp at 3300 comes in at 31 lumens/watt (add 6 l/w for the 200 K rise). That's pretty darn close, isn't it. Plus, look at the life rating. 20 hours of life.

See the difference? WA1111 at 3325 K gives 100 hours, but a Carley 852 at 3100 K gives 20 hours? Say what? Something is definitely wrong there, isn't it? And if it were going to be skewed in one direction or the other, it should be skewed IN FAVOR of the 852, which is xenon filled and thus suppressed vaporization of the filament better than the Krypton fill of the WA lamp.

So, what I'm getting at here, is that the CCT of a lamp is something difficult for us to measure, or calculate, based upon the information we have. The best we can do is compare known sources (from integrating spheres) against unknown ones, via the good ole eyeball. And doing so, I can say that the Welch Allyn 1111 at 6.0 volts is no friggin 3325 K filament. Not if the A2 is. Because the A2 is whiter than the 1111 at 6 volts. Noticeably whiter.

So, I don't think it's any accident that there isn't any formula for deriving CCT from volts, amps, and filament geometry. If the filament were a nice sphere instead of a helix, and if you could ignore convective cooling and assume a pure blackbody in a vacuum with no reflected radiation, then you can do it pretty easily. But the fact is that

1. A filament coil is a whole lot more complicated, and has a temperature which varies with spatial location.

and

2. Convective cooling will depend upon the pressure and composition of the gas mixture, and the shape of the envelope and filament and support wires and so on.

However, if anyone thinks he or she can do it, I would absolutely LOVE to see a formula for the CCT of a filament based upon the voltage, current, and geometry. Then let's try it out on some known lamps. Or even throw in hours of life as a known variable. Even then, I doubt it could be done.

Anyway, as I said at the start, I will be putting together a primer-type thread on Lamp Physics at some point. So if I am in error on any of this stuff, let's work it out now, before I start working on the final version of that.


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## PANZERWOLF (Dec 6, 2006)

js said:


> A smooth, vacuum aluminized reflector with a Welch Allyn 01274 lamp potted into it was sent to an integrating sphere to be measured for total beam lumens, or MSCP (=total lumens/4 pi). This lamp is rated at 553 lumens at 7.2 volts. 7.2 volts was applied at the pins and 391 lumens was measured in the sphere.


i don't want to be picky, but i wouldn't underestimate the difference between being "rated" and being measured in your sphere, so i think that measuring both with and without reflector could have given a bit different numbers


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## bwaites (Dec 7, 2006)

Newbie,

Actually the AR coatings I was talking about are those used on the UCL lenses.

They literally bake off if left too close to the lamps, I have found this to be the case even with a 1499 run in a MiniMag. 

Somewhere I have a UCL lens that has no coating in the center, (it's quite easily seen, looks like a donut). 

As far as other coatings, I defer to your superior knowledge!

What I have observed is two things:

The glass shatters at high temps, OR, the AR coating bakes and vaporizes leaving a funky uneven covering, and then eventually the glass shatters.


Bill


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## js (Dec 7, 2006)

PANZERWOLF said:


> i don't want to be picky, but i wouldn't underestimate the difference between being "rated" and being measured in your sphere, so i think that measuring both with and without reflector could have given a bit different numbers



The 1274 was driven at the rated voltage, so I think it's safe to trust the manufacturer's MSCP rating on this.

But, if you want to PayPal me $125 I will have them test a bare 1274 at 7.2 VDC for us.


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## woodrow (Dec 12, 2006)

js. I will be brief because I am WAAY out of my depth in this discussion...But I wanted to say thanks from myself and most likely some of the other non scientists here.

I just bought a gl4 with a "550" lumen lamp. It is very bright and I like it a lot, but it does not seem much brighter than my 10 watt hid. The hid supposibly has a "500 luman" bulb as well, but I have read a post from a person who has both my hid light and a M6, and the M6 was reported to be easily brighter.

Basicly to me, your 65% information helps me solve a mental problem I have been having. It also makes me proud of Surefire for posting torch lumens instead of bulb lumens. 

So as I understand all this---My gl4 and lc100 are producing around 360 lumens more or less at the front end of the lights. If I want to spend $380.00 additional I can have a M6 that will be brighter than both-using 6 batteries for 20 minutes.

All of this makes me feel better because the mighty M6 is not beaten by my $86.00 light, but lumans per dollar, I did ok.

Ok, I will leave now and go take some excedren with some crown royal so I can forget all that metal coating and refracting stuff. Thanks for the info though.


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## NewBie (Dec 25, 2006)

bwaites said:


> Newbie,
> 
> Actually the AR coatings I was talking about are those used on the UCL lenses.
> 
> ...




Do you find that borosilicate/borofloat also shatters? Glasses like Pyrex are made from this stuff, and are used for cooking ware and even lab beakers that you put on bunsen burners.

As I recall, Silicon Dioxide AR coatings are more durable to high heat and a bit more rugged. They will typically have a greenish tint, where properly applied Magnesium Flouride has a purplish tint under strong light.


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## NewBie (Jan 9, 2007)

Okay, so in a nutshell, after all the genuflecting the 65% conversion factor was confirmed for reflector and lens losses thru actual measurement.

If my memory serves correctly, Gransee's integrating sphere tests confirmed also that mineral glass adds 14% loss to the equation, refering to the HDS light that had the sapphire/mineral glass lens installed 50 lumens, then it was removed and measured 57 lumens.

Andrew-
Yes, how much of the exiting light hits the reflector surface should definitely have a large play on things, as the reflector coatings used in flashlights are quite lossy.

bwaites-
Did you catch my last post yet?


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## bwaites (Jan 9, 2007)

Thanks Newbie, just saw it.

I haven't had any Boro lenses shatter from heat, it's why I used them in the USL.

The UCL lenses aren't Boro, though. flashlightlens.com did have some heat strengthened UCL lenses, and I didn't have them shatter, even in USL's, although the antireflective coating did disintegrate over a few sessions.

Bill


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## NewBie (Jan 12, 2007)

Good to know.

Sure would be interesting to try the Silicon Dioxide based AR coatings, since they are much more durable under heat, as compared to Magnesium Fluoride. Of course, not all Magnesium Fluoride AR coatings are equal either.


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## Art Vandelay (Apr 7, 2007)

I learned a lot from this thread. Lots of people are comparing bulb lumens and out the front lumens as if they were the same thing. I still prefer a FlashlightReviews.com style light box measurement to get estimated lumens, but if you can get an accurate rating of a bulbs lumens, the 65% rule of thumb seems to work very well.

For the most part, this thread is a good example of people arguing the science and not getting bogged down with personal attacks.


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## js (Apr 7, 2007)

Thanks, Art!

I'm afraid I am responsible for a lot of the in-fighting that went on in the middle part of this thread! But, it settled down after that.

And yes, absolutely, a lumens box estimator is a way cool device. Along with ceiling bounce methodology and other methods for trying to quantify what the output of a light IS, and how it compares to other lights, and so on. The amazing thing is that various CPFers managed to narrow in on the 65 percent figure, and it allows creators of many mods to go from bulb lumens to torch lumens with a reasonable amount of accuracy. This benchmark figure was attacked pretty hard by Luna back in one of Lux Luthors early threads in the general forum, and I was the one arguing with him. And so when he popped in early on and acted so cavilier about accepting it, I got more than a little steamed about it. My bad! But, as I said, we moved on to more productive discussion.


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## Luna (Apr 10, 2007)

> This benchmark figure was attacked pretty hard by Luna back in one of Lux Luthors early threads in the general forum



Never attacked, only questioned since it was never confirmed...to that point


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## js (Apr 10, 2007)

Hey Luna! How are you?

Yeah. You're right. But I took it as an attacking kind of questioning at the time, hot-head that I am. Sorry.

BTW, please go back about a dozen or so posts and read my comments on CCT as measured by Carely vs as measure by Welch Allyn! I was hoping you would give me your thoughts back when I first made those posts. Post #100 in this thread is what I am refering to, mainly. Check it out, and let's see what we can figure out! I'm still pretty far away from having my lamp physics thread ready, so I could use your opinions on this. Let me know.


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## LED61 (Apr 10, 2007)

I just read this entire thread as I had missed it previously. Thanks Jim and Newbie, another ton of good info learned!!


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## Luna (Apr 10, 2007)

js said:


> Hey Luna! How are you?
> 
> Yeah. You're right. But I took it as an attacking kind of questioning at the time, hot-head that I am. Sorry.
> 
> BTW, please go back about a dozen or so posts and read my comments on CCT as measured by Carely vs as measure by Welch Allyn! I was hoping you would give me your thoughts back when I first made those posts. Post #100 in this thread is what I am refering to, mainly. Check it out, and let's see what we can figure out! I'm still pretty far away from having my lamp physics thread ready, so I could use your opinions on this. Let me know.



With a four almost five month old in the house, I've missed a bunch  Hehe I just enjoy debating/playing anyways, as do alot of us as I can tell...that is part of the fun... so hopefully nobody will take me as an *** as I can sometime seem. 

I'll try to catch up on the articles, so if anything else big has come about lately point me in the direction.

Take care!

-Craig


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## js (Apr 10, 2007)

PANZERWOLF said:


> js said:
> 
> 
> > A smooth, vacuum aluminized reflector with a Welch Allyn 01274 lamp potted into it was sent to an integrating sphere to be measured for total beam lumens, or MSCP (=total lumens/4 pi). This lamp is rated at 553 lumens at 7.2 volts. 7.2 volts was applied at the pins and 391 lumens was measured in the sphere.
> ...



I've been thinking some more about this, and I actually think that it was _more_ instructive to use the _rated_ lumens of the lamp as given by Welch Allyn, compared to the _measured_ lumens, because _*everyone is using the WA ratings (or re-ratings)*_ and very few people (if any) are able or willing to measure bulb-lumens in an IS to start with.

So if there is any systematic difference between the two: WA ratings/re-ratings bLu vs. measured bLu, we want to go with the one _that people will be using_ and adjust from there in order to come up with our transmission efficiency.

However, all of that said, I agree that ideally, we would measure the bare lamp, then the lamp in a reflector, then maybe even the LA in a flashlight with various lenses, and all that. But, hey, I'd like to get IS measurements of all the various SF M6 LA's at start, 5 minutes into, middle, and end of, run, but that's not going to happen anytime soon. That would cost,  , on the order of $1,200, not counting the batteries.


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## js (Oct 17, 2007)

I still plan on someday doing a thread on the physics and design of tungsten halogen low-voltage lamps, but I really haven't made much progress in the way of actually starting a draft of the thread, or even collecting some in-house manuals and documentation from, say, Carley and Welch Allyn. However, I've got to do some dealings with Carley in the next week or two and I may ask their lamp engineer to send me that stuff. He had at one time promised to do so for me, but never did and I never bothered him about it as I was busy with other things. But, I really would like to collect together all the stuff to make a lamp physics thread, which will cover all the basics, as well as things like quartz glass vs. hard glass envelopes, IRC coatings, and so on.

And, I also just wanted to bump this thread to the top again. Been a while since it was there.


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## DM51 (Oct 17, 2007)

Thanks for bringing this one up again, js - it's well worth a re-read. 

If you come to do something on the physics, Ra posted some interesting stuff in this thread about reflector absorption, coatings, TIR efficiency, etc etc.


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## LuxLuthor (Oct 17, 2007)

I miss NewBie. :bow:


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## jimjones3630 (Oct 17, 2007)

Pretty interesting stuff. A bit over my head but glad someone is working on this.

Does "[FONT=VERDANA, ARIAL, HELVETICA][COLOR=#0]*UCL® Lens '*Water white' glass with a high performance anti-reflective coating on both sides." coating burn off with 100w mods common here?[/COLOR][/FONT]

thanks jim


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## js (Oct 17, 2007)

jimjones3630,

No. The AR coating stands up. The problem is that the glass itself sometimes doesn't. UCL's will sometimes crack due to the intense heat and IR. The borofloat glass is the material of choice for high powered incan mods, and has proven that it can stand up to repeated 100W or higher burns without cracking.

DM51 & LuxLuthor,

My lamp physics thread won't have any information on coatings and reflectivity and reflectors and all that stuff. It will be purely about the lamp and its components and the physics underlying it all--CCT, I-V, temperature, fill gas, etc., characteristics.

Besides, as LuxLuthor points out, NewBie already covered a lot of the ground on geometrical optics and coatings and efficiencies and all that. These posts/threads still exist and can still be read.


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## bwaites (Oct 17, 2007)

js and jimjones3630,

I have had both positive and negative experiences with UCL coatings.

I actually have had the UCL coating melt off of lenses, particularly the hotter minimag mods where a 1411 Carley is used run by AA LiIon cells.

But I have also had long run 100 watt 64625 Osrams do the same to full size Maglite lenses. 

For short runs they seem fine, but prolonged, repeated runs with the larger high output lamps can cause some disintegration. I have not had it happen with a 62138, interestingly, only with the larger 64625 and similar lamps.

I have, however, shattered several UCL lenses with both the 62138 and the 64625 lamps, as well as an overdriven 64623. 

As js notes, the borofloat lenses do a better job of taking the intense heat.

Bill


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## jimjones3630 (Oct 18, 2007)

lens and bulb held up tonight but the reflector sad to say did not.

64458 90w with 5xemoli 21v hot off charger within 10sec the reflector blistered up like a bad case of chicken pox. It was amazing to watch. 

Have not broke any lens to date, have a couple of UCL came with lights I bought. They are mixed up now with boros and don't know how to tell them apart.


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## LuxLuthor (Oct 18, 2007)

Never had a boro lens crack from any of my 90W+ hotwires. JJ, if you had a metal reflector do that, IMHO, there is something wrong with it. What brand (& surface) of reflector & who made it? To date, I have never had a problem with any of FM's metal reflectors in any size, nor the 3" Carley that Delghi recently provided.


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## js (Oct 18, 2007)

Actually, SilverFox had a bad experience with a mag mod with a Carley reflector. And, IIRC, Bill Waites was the maker of the mag mod--do you remember this, Bill?

Anyway, evidently what happened was that there was some kind of water or moisture in the undercoating layer, and when run hot, drops of water would form, fall on the bulb and break the envelope. It was a defective Carley 1940, and as soon as Tom replaced that, everything was fine. It was freaky, though. I was sure the moisture was coming from the PR base potted WA lamp potting material. I never would have guessed it was coming from the *reflector*. So maybe something similar here?

I, like LL, have never experienced something like that--no blistering or cracking or anything--with a Carley reflector, or a MagCharger reflector. Although . . . come to think of it, my first SF M6 turbo head reflector actually had a spot of the OP coating "melt" and form a flat circular spot on the reflector. I couldn't believe it! And neither could Willie Hunt. My guess is that it was the undercoating that became fluid and flattened out, and the vacuum aluminizing just followed it. Then I exploded an MN20 in that Turbo Head, and SF warranteed it.

As for telling boro and UCL apart, try cleaning them carefully, then look at them obliquely and notice the color of the reflections of things. The UCL with AR coating will have a green or blue tint, and a faintness to the reflection, whereas the boro will act a lot more like normal glass.


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## jimjones3630 (Oct 18, 2007)

js thanks for the info. This reflector blistered uniformly around and bottom to top. when it was still hot the blisters were bigger. Looked like could have pealed the whole coating off. I believe Carley is the maker of this reflector.


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