# So I bought some LEDs... (part le deux)



## fyrstormer (Dec 14, 2009)

...because I heard the Luxeon line was being discontinued, and at least the one place I looked didn't have any Rebels in a similar format, brightness, or power-handling capacity, so I figured I'd better grab a few while I still could. You know...just in case. 







I really like Luxeons. 

So what's the deal with Rebels? I didn't see any that could handle more than ~500mA or were rated higher than ~80lm. Is Philips bailing out of the high-power single-emitter market? The Rebels all look like they're intended for use in unfocused arrays. Given my experience with putting a Luxeon K2 in my Arc6, the Luxeon line is just as effective as anything Cree or SSC has to offer; they can't be getting burned _that_ badly by market competition...are they?


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## was.lost.but.now.found (Dec 14, 2009)

fyrstormer said:


> I really like Luxeons.


 
I'll bet you miss Beta tapes also. The market really missed out when VHS took over.


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## asdalton (Dec 14, 2009)

fyrstormer said:


> Given my experience with putting a Luxeon K2 in my Arc6, the Luxeon line is just as effective as anything Cree or SSC has to offer


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## yellow (Dec 14, 2009)

> they can't be getting burned _that_ badly by market competition...are they?


really, I wonder if that is a troll thread, or not
:thinking:
anyone knows what output an XR-E gives at 1500 mA?
or, better, what current it might need for 250 datasheet lumen, like stated in that order paper for the led?
or what current an XP-G needs for 250 lumen?

all that money 
btw.: those prices for led - 3-4 years old like the "V" - they are not very good.


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## fyrstormer (Dec 14, 2009)

Luxeons are just as bright as contemporary Cree and SSC emitters, with a higher CRI than both, they just need a bit more power to do it. They tolerate overdriving much better than SSC emitters do, to boot. Flashaholics might have been infatuated with Cree's higher output-per-watt and higher output-per-dollar to begin with, but now that every light on the market is way too bright for anything but foot-candle drag racing, people are starting to remember how nice it is to have a beam that _fully_ illuminates what it's aimed at.

But as has been mentioned many times before, flashlights are a small minority of the LED market as a whole, and I guess Philips thinks the future is lots of tiny, redundant emitters. I guess they aren't wrong, but it's sad to see them discontinue the original line of high-power emitters. There's gotta be more uses for them than just pocket rockets.


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## fyrstormer (Dec 14, 2009)

yellow said:


> really, I wonder if that is a troll thread, or not


Oh don't worry, it's not a troll thread. This isn't the first time I've casually made a remark that other people thought was outrageous, but I'm just saying it because I think it's true.



yellow said:


> btw.: those prices for led - 3-4 years old like the "V" - they are not very good.


The cyan ones were expensive, because the place only had a couple dozen left in-stock, but the rest were pretty cheap.



yellow said:


> anyone knows what output an XR-E gives at 1500 mA?
> or, better, what current it might need for 250 datasheet lumen, like stated in that order paper for the led?
> or what current an XP-G needs for 250 lumen?


Copped from the K2 TFFC datasheet:






I couldn't find a similarly-comprehensive listing for Cree XR-E's (which is the only valid comparison, since the XP-G is about a year newer than the K2), but from what I could divine, the Q5 was are rated up to ~230lm @ 3.7v x 1.0A, which is about on-par with the cool-white Luxeon K2. And the K2 still has a higher CRI rating than the Q5.


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## mds82 (Dec 14, 2009)

wow.... thats a lot of money for not many LED's....


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## fyrstormer (Dec 14, 2009)

Well, it's 19 of 'em, and they're all the brightest in their categories that I could find, so it's not that bad. I could've gotten better prices if I'd bought them by the reel, but that's WAY more than I will ever use. This is just a stash in case I come across any worthy SSC- or Luxeon-based lights in the future that could use a good upgrade, since these may well be the penultimate version that's compatible with the optics on older lights, what with everyone switching to the new small-footprint emitters. I don't want to have to mess with focal lengths if I don't have to.


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## blasterman (Dec 14, 2009)

Is somebody practicing April 1 posts?

Seriously fyrstormer, I just completed a interiour lighting project with a mix of Rebels and Crees from LedSupply, and the $6 neutral white rebels I got put out 100lumens at 350mA, and those were mediocre flux. They put out 180 lumens at 700mA, so how much do your LuxIIIs put out again?

Some of the posted specs you have for colored Lux IIIs and V's get their nads handed to them by the stuff I'm buying from BestHongKong, which, you guessed it, is why I no longer buy Luxeons.

While the K2 has respectable current handling specs it was rendered totally obsolete by the XP-G, and Phillips knows it.

But then again, if you think a cool white Lux III has great color there's no point arguing with you.


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## fyrstormer (Dec 14, 2009)

blasterman said:


> Is somebody practicing April 1 posts?


No.



blasterman said:


> Seriously fyrstormer, I just completed a interiour lighting project with a mix of Rebels and Crees from LedSupply, and the $6 neutral white rebels I got put out 100lumens at 350mA, and those were mediocre flux. They put out 180 lumens at 700mA, so how much do your LuxIIIs put out again?


You'll notice I didn't buy any white Lux3's. The whites are all K2's, and the neutral-white ones I got come out at 150-170lm @ 700mA, and they were $4.50 apiece. I'm not surprised the Rebels can achieve better flux per watt, being newer, but again, not the same overall output, hence the dismay that their line of LEDs that _can_ reach that output are being discontinued.



blasterman said:


> Some of the posted specs you have for colored Lux IIIs and V's get their nads handed to them by the stuff I'm buying from BestHongKong, which, you guessed it, is why I no longer buy Luxeons.


Oh well. Live and learn. But like I said, I really like Luxeons.



blasterman said:


> While the K2 has respectable current handling specs it was rendered totally obsolete by the XP-G, and Phillips knows it.


I guess. But why they're giving up on the single-unit high-power form factor _entirely_, I don't understand.



blasterman said:


> But then again, if you think a cool white Lux III has great color there's no point arguing with you.


Only the single-colors are Lux3's and Lux5's, and as I'm sure you're aware, tint is a complete non-issue with single-colors -- or rather, if you're making an issue of it, you're setting yourself up for disappointment.

- - -

For reference, here is a picture of the neutral-white K2 in my Arc6, next to a Cree XP-E R2 in a Lummi Raw and an OSRAM Golden Dragon. Ignoring brightness, since the Raw is direct-drive and so there's no guarantee it's pulling the same current (though the batteries were all fresh), tell me which has the best tint.


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## spencer (Dec 14, 2009)

Your first thread was closed for a reason. I don't know why you reposted but this thread definitely seems like a troll/advertisement.


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## John_Galt (Dec 14, 2009)

I suppose you had your reasons, but, really, newer LED's from Cree and SSc have replaced Luxeons for a reason.

I mean, if you had a few light that used Luxeons, or had a light that has shown to work well with a K2, I could see buying a few for future projects, but, come on... $180+ for outdated LED's? When Cree's are $3-5? I just don't understand your logic.


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## Th232 (Dec 14, 2009)

fyrstormer said:


> I couldn't find a similarly-comprehensive listing for Cree XR-E's (which is the only valid comparison, since the XP-G is about a year newer than the K2)...



I think this is kinda the problem here, you're comparing two LEDs from a certain timeframe, and then based on those results extrapolating to say that Luxeons are still as bright. While they were sort of comparable then, you're ignoring advances in technology since then (namely by Cree), which is where your logic breaks down.

As for colour rendition, I think that's one area that we can partially agree on, but that still heavily depends on what tint bins you get.

For the record, from Cree's datasheets, a Q5 is ~240-256 lumens at 1 A, if my counting system is right.

Out of curiosity, how do you think that a Luxeon fully illuminates something that a Cree or SSC doesn't? From what I can see, that's mostly a matter of optics and output, the former can be changed easily for a wider optic, and the Luxeons are getting stomped on in the output arena. An XR-E might have a tighter beam distribution, but the XP-G pretty much has a Lambertian distribution, and greater output.


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## fyrstormer (Dec 14, 2009)

John_Galt said:


> I suppose you had your reasons, but, really, newer LED's from Cree and SSc have replaced Luxeons for a reason.
> 
> I mean, if you had a few light that used Luxeons, or had a light that has shown to work well with a K2, I could see buying a few for future projects, but, come on... $180+ for outdated LED's? When Cree's are $3-5? I just don't understand your logic.


As it happens, I do have a bunch of lights using SSC LEDs now, and there are plenty of older lights with Lux3's in them that could use an upgrade. Since Cree can't seem to get their heads on straight about making LEDs with standard lambertian dispersion patterns (probably because that makes them better candidates for household area lighting without needing bulky optics), that rules them out as an upgrade path for lights with "normal" reflectors. Meanwhile, SSC uses a phosphor formulation that is very sensitive to overheating, hence why the Arc6 has an advisory that the highest setting should only be used sparingly. Now my Arc6 can run on Level 7 until the battery gives out without any ill effect to the emitter.

Frankly, I just haven't seen a beam from a Cree light that was as pleasing to look at as what I've seen from the K2. I have the same complaint about Cree LEDs as I have about cheap fluorescent lightbulbs -- the brightness in just a few colors of the spectrum, combined with almost complete darkness throughout the rest of it, makes my eyes hurt. I have a halogen lamp sitting on my office desk for that very reason -- to fill in the gaps in the spectrum so I don't get a splitting headache every single day from the combination of cheap fluorescent bulbs and my computer screen. The K2 has a much better phosphor formulation in that regard. The Rebel might eventually replace it as being just as bright, but not yet, and it's the wrong size to upgrade older lights with anyway.

Once again, the K2s I bought were $4.50 apiece. That pricing is competitive with what Crees cost from wherever it is you buy them.


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## spencer (Dec 14, 2009)

fyrstormer said:


> the Arc6 has an advisory that the highest setting should only be used sparingly. Now my Arc6 can run on Level 7 until the battery gives out without any ill effect to the emitter.



Now all your logic is gone. I don't know anything about the Arc 6 but I can make the assumption that it uses a constant current driver. 
Say level 7 is 700mA. With a SSC lets say thats 150 otf lumens. A Luxeon at 700mA would be lucky to get 100. 
Say level 6 is 500mA. A SSC is still brighter than the Luxeon at level 7.

Just cause you want to run your light at max power doesn't mean it will be as bright as it can be.


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## Th232 (Dec 14, 2009)

fyrstormer said:


> Since Cree can't seem to get their heads on straight about making LEDs with standard lambertian dispersion patterns (probably because that makes them better candidates for household area lighting without needing bulky optics), that rules them out as an upgrade path for lights with "normal" reflectors.



Come again?

https://www.candlepowerforums.com/posts/3192876&postcount=630


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## fyrstormer (Dec 14, 2009)

Th232 said:


> I think this is kinda the problem here, you're comparing two LEDs from a certain timeframe, and then based on those results extrapolating to say that Luxeons are still as bright. While they were sort of comparable then, you're ignoring advances in technology since then (namely by Cree), which is where your logic breaks down.


I never said the K2 is just as bright as newer Cree emitters -- I said the newer Cree emitters are invalid for comparing directly against the K2, and the newer small-footprint emitters won't work in older lights with reflectors designed for larger emitters.



Th232 said:


> As for colour rendition, I think that's one area that we can partially agree on, but that still heavily depends on what tint bins you get.


Not really. CRI is based on how accurately an emitter renders a test color pattern _as compared to a hot-black-body light at the same temperature_. CRI is an issue of spectrum fullness, not spectrum balance.



Th232 said:


> For the record, from Cree's datasheets, a Q5 is ~240-256 lumens at 1 A, if my counting system is right.


Maybe so, but they get it by using cheaper phosphors, hence why every Cree I've ever seen has a greenish fluorescent tint to it. Occasionally I see one with a snow-white tint, and that's much nicer, but the green-white tint gives me a headache. And anyway, the brightest Luxeon K2 is their _neutral-white_ emitter, not their _cool-white_ emitter. Cree couldn't beat that at the time, and as far as I've seen, they still can't.



Th232 said:


> Out of curiosity, how do you think that a Luxeon fully illuminates something that a Cree or SSC doesn't?


I'm not talking about beam dispersion, I'm talking about CRI. See above.



Th232 said:


> the XP-G pretty much has a Lambertian distribution, and greater output.


Well, that's better, but why do the newer Crees still have rings when you put them in normal reflectors? Personally, I can't decide whether they're doing it to narrow the beam because they think they think a tighter beam is more useful, or to artificially generate a market for Cree-specific optics.


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## fyrstormer (Dec 14, 2009)

spencer said:


> Now all your logic is gone. I don't know anything about the Arc 6 but I can make the assumption that it uses a constant current driver.
> Say level 7 is 700mA. With a SSC lets say thats 150 otf lumens. A Luxeon at 700mA would be lucky to get 100.
> Say level 6 is 500mA. A SSC is still brighter than the Luxeon at level 7.
> 
> Just cause you want to run your light at max power doesn't mean it will be as bright as it can be.


Level 7 on an Arc6 is 1400mA. A Cree running at that current will blue-shift, and an SSC P4 will burn its phosphor in a few hundred hours at that current.

Also, based on _the datasheet which I provided_, the K2 I installed in my Arc6 matches the SSC P4's output of 150lm @ 700mA, _and_ it does it with a warmer tint and higher CRI.

Say what you want about my logic, but at least I know the background info about my examples. Where are you getting _your_ numbers from?


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## fyrstormer (Dec 14, 2009)

Th232 said:


> Come again?
> 
> https://www.candlepowerforums.com/posts/3192876&postcount=630


Well, good. It's about time they got with the program. I won't argue about beam-dispersion patterns anymore, except perhaps as applies to retrofitting older lights with newer emitters, which is _the intended purpose of my purchase_.


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## DM51 (Dec 14, 2009)

spencer said:


> Your first thread was closed for a reason. I don't know why you reposted


This thread can continue if it remains within the Rules.


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## Th232 (Dec 14, 2009)

Fair points on the CRI, and thanks for clarifying exactly what you meant by "fully illuminating", seems that we have different definitions. Out of curiosity, do you have a numerical value for the CRI? Someone's wanting to create a list of high CRI LEDs, and I'm interested to know how they compare to the usual Nichias and SSCs.



fyrstormer said:


> Maybe so, but they get it by using cheaper phosphors, hence why every Cree I've ever seen has a greenish fluorescent tint to it. Occasionally I see one with a snow-white tint, and that's much nicer, but the green-white tint gives me a headache.



Interesting, only Cree I've ever seen with a greenish tint was in my Ti Quark. I suppose we've got different eyes? Also, got a source about the cheaper phosphors? That part surprises me, and I'm genuinely curious.



fyrstormer said:


> Well, that's better, but why do the newer Crees still have rings when you put them in normal reflectors? Personally, I can't decide whether they're doing it to narrow the beam because they think they think a tighter beam is more useful, or to artificially generate a market for Cree-specific optics.



Funny, I've never seen ringed beams from the XP-Gs (assuming that's what you mean when you say "newer") unless you just jam them in there without any regard to the focal point of the reflector/optic in question, but from what I can see that's a general issue that happens to some degree between any two LEDs, even if you're swapping Luxeons with SSC P4s. Only a small amount, maybe 30 mils, but still required for perfect focus. 

If by "newer" you're referring to XR-Es, the rings were a side-effect of the metal collar, which was to create a tighter beam. Think that was for the former reason.



fyrstormer said:


> Well, good. It's about time they got with the program. I won't argue about beam-dispersion patterns anymore, except perhaps as applies to retrofitting older lights with newer emitters, which is _the intended purpose of my purchase_.



Fair enough, but a small correction for the record, unless I'm greatly mistaken, XP-Es have been out for some time...


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## asdalton (Dec 14, 2009)

My Quarks with XP-E and XP-G emitters have no rings in their beams at all. And the XP-G light uses a smooth reflector.


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## Benson (Dec 15, 2009)

spencer said:


> Now all your logic is gone. I don't know anything about the Arc 6 but I can make the assumption that it uses a constant current driver.
> Say level 7 is 700mA. With a SSC lets say thats 150 otf lumens. A Luxeon at 700mA would be lucky to get 100.
> Say level 6 is 500mA. A SSC is still brighter than the Luxeon at level 7.
> 
> Just cause you want to run your light at max power doesn't mean it will be as bright as it can be.


These go to eleven.



fyrstormer said:


> Level 7 on an Arc6 is 1400mA. A Cree running at that current will blue-shift, and an SSC P4 will burn its phosphor in a few hundred hours at that current.


Way to miss the point entirely -- more efficient LEDs don't _need_ to run that current to match the output, so how long they'd last at those levels isn't horribly relevant.



> Also, based on _the datasheet which I provided_, the K2 I installed in my Arc6 matches the SSC P4's output of 150lm @ 700mA, _and_ it does it with a warmer tint and higher CRI.


What bin are you comparing against? (I must have missed where you provided a P4 datasheet...) AFAIK, cool P4s are available in U-bin, which will make 150 lumens at only ~550mA, you'd need at least 170lm@700mA to match them. But I know neutral P4s have a much bigger efficiency penalty vs. neutral Crees, so your K2 probably still beats them.


I'll admit I'm not horribly familiar with the SSCs, let alone neutral SSCs, so I'm going to focus on the Crees here, with numbers mostly from jtr1962's white LED testing thread:

At 1.4A, a 180-bin K2 only makes 235 lumens. A Cree Q5 makes that at 1A. IIRC, neutral tints are only generally available up to Q4, so maybe 1.1A... So it doesn't matter what the Cree does at 1.4A, because you'll match that while using _less_ power. If the _extra_ bright option of level 7 _does_ shift cool, you can simply not use it unless/until you find yourself in a position where output becomes more important than tint. Unless level 6 is below 1A (and I don't know, but would be surprised if this were the case), you'll get practically equivalent light the rest of the time.

Not being a warm-white fan, I only have one neutral light, a Mag with an XR-E. And I don't see any tint-shift going from 1A to 1.4A, although kicking it up to ~2A goes rather cool. Of course, as this is heat-related, these results are not generally applicable, and I don't really know how good the Arc6 is thermally, but unless you have tried an XP-E in a comparable light, I see no reason to assume it's that bad, especially if carefully upgraded.

I can't see why an XP-E would be any worse than the K2 in that application, and the XP-Gs (when warmer tints arrive, should be soon) would be a _serious_ upgrade. (As to whether it's "fair" to compare K2s to XP-Gs -- you're not buying these back when K2s came out, you're buying them now. Since the neutral XP-Gs haven't hit yet, they're not quite a fair comparison, but cool XP-Gs and neutral XP-Es definitely are.)

Of course, the different manufacturers use different phosphor setups, with resulting different spectra and CRIs, so if you still need the K2s to make your eyes happy, that's fine, but unrelated to whether or not you can use level 7.


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## blasterman (Dec 15, 2009)

> I'm not surprised the Rebels can achieve better flux per watt, being newer, but again, not the same overall output, hence the dismay that their line of LEDs that _can_ reach that output are being discontinued.


 That's about the only valid point you make. Again, I have little issue with the TFFC K2 and am scratching my head a bit at Phillips on this one, but your hand-springs over the Lux III are, with due respect, delusional.



> Only the single-colors are Lux3's and Lux5's, and as I'm sure you're aware, tint is a complete non-issue with single-colors -- or rather, if you're making an issue of it, you're setting yourself up for disappointment.


 
I work with interiour lighting where color consistency is a critical even if it's white or colored. First lesson I learned in Lux IIIs have sucky bin consistency with their blues ranging from average blue (460nm) to downright cyan (+490). This is when I stopped using them.

This was the major reason I started using Chinese power emitters because I didn't want to use Cree due to prices. Not only have I found most colored Chinese emitters more consistent than Lux IIIs, they are cheaper, and brighter, and have better color. K2's aren't exactly amazing in the colored dept either, other than red which is competitive, but they are better than Lux IIIs.

Pretty sad when Chinese emitters are beating your product.



> tell me which has the best tint.


 
How long is a piece of string? First, when I test colors with an emitter I shoot RAW with my dSLR and not white walls with JPGs and sRGB mode. Next, I work with interiour lighting where color consistency and CRI is very critical - I don't shine flashlights on white walls which proves nothing either than a relative CCT comparisons and what pigments are in the paint used to reflect the light source off of.

The neutral white Bridgelux I use are far, FAR more consistent in both color white and neutral bins than Cree, K2 or Lux III combined because they have to contend for the high demands of interiour lighting. However, you can't use a Bridgelux in a flashlight dsigned for Lux IIIs. Conclusion: Bridgelux sucks?

Cool white Lux III have flat out terrible color rendition, and while cold white emitters of all manufacturers are weak in this respect due to lack of the additional phosphors, K2s and Crees are certainly better than Lux III. Light bars I've built with Lux IIIs a few years ago because I didn't know what I was doing have been upgraded to Cree because customers couldn't stand the anemic color rendition of Lux III. Cool white Crees and K2 are at least tolerable.

It appears your main justification for Lux III's, and emitters in general is that they work good in your flashlights and appear neutral when shined on white acrylic paint. As I've informed other people in this forum, Cree, Phillips and the rest don't care about how their emitters project on a wall when mounted in a flashlight with optics designed by third party sources. 

Evaluating an LED on the basic of how it works with your existing flashlight optics would be like evaluating computer processors on the basis of how they work with prior socket configs. The optics should be tailored to match the emitter and desired beam dispersion, not the other way around. Precision acrylic optics I've been using lately for Cree are also about 1000x more numerous and diverse (and better quality) than I'm finding for Lux III or K2 or Rebel for that matter.


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## yellow (Dec 15, 2009)

1st: 
luxeon lottery = *tint* ... when not to be chosen be4 ordering, talking about after purchase makes no sense
(f.e. I once ordered 2 identical Rebel lights - have been said to be "sooooo nice tint" - one did give a tint that was ok, the other one was angry blue.
Was I disappointed? Yes.
Did I blame the led/light maker? No, because there was no tint specified, so ...)

2nd: 
ringy beam = cheap focusing device.
cram an XR-E into a Sandwich Shoppe reflector and be surprised.
also that is the only Cree led that makes the Cree ring, with any other led it is the cheap focusing device creating them

3rd: 
when a led needs ~1.5 times the current, to be in the same output class, there is no discussion,
especially in battery powered application


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## fyrstormer (Dec 17, 2009)

I don't much feel like continuing the argument, but you may be interested to know that I originally found the vendor where I bought these emitters via a conversation I had with Curt from Peak LED Solutions -- he actually suggested the K2s as an upgrade for the lights I have that run on P4s (as well as older Luxeons, obviously) for the reasons I listed previously.


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## John_Galt (Dec 17, 2009)

It doesn't have to be a disagreement. You've told us your opinion, we've told you ours, we don't necessarily like what the other has to say.

This is entirely opinion based, to a certain degree.


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## JFD140 (Dec 17, 2009)

I win... Are they seriously going out of business? PLEASE say that isnt true... Gonna cost me $1300 if they seriously are...


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## fyrstormer (Dec 18, 2009)

Is who going out of business? Are we talking about the shop you and I bought from, or Philips Lumileds?


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## JFD140 (Dec 18, 2009)

lumileds... obviously Philips will never go out of business.

But they aren't seriously not gonna make the rebels anymore right?


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## spencer (Dec 18, 2009)

They are still making rebels, they just discontinued the Lux 1/3 for sure and maybe (don't really remember) the K2 and Lux 5. Someone should clarify this.


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## fyrstormer (Dec 18, 2009)

I...didn't say the Rebels were being discontinued. I said the Luxeons were being discontinued.



spencer said:


> They are still making rebels, they just discontinued the Lux 1/3 for sure and maybe (don't really remember) the K2 and Lux 5. Someone should clarify this.


It's in the first line of my first post! How much more clarity is needed?



fyrstormer said:


> ...*because I heard the Luxeon line was being discontinued*, and at least the one place I looked didn't have any Rebels in a similar format, brightness, or power-handling capacity, so I figured I'd better grab a few while I still could.



Nobody's actually reading anything I write, are they? Maybe that's what's wrong here.


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## JFD140 (Dec 18, 2009)

ooooo thank god lol. You scared me like you could not imagine.

Would really suck if they just discontinued the LEDs i based a $4000 prototype around...


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## fyrstormer (Dec 21, 2009)

Wow, um...the cyan Lux5's are really bright. Did you know they're quad-die? I was testing one with various types of batteries and even a fully-charged Ultrafire was barely lighting it up (like, I could still see the gallium nitride through the haze of photons), and finally I said to hell with it and hooked it up to an Ultralife lithium 9V. However, when I did this I had it pointed at my face, so I could see whether it lit up at all because I was concerned it was defective.

It is most certainly NOT defective. My vision might recover one of these days.


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## Benson (Dec 21, 2009)

fyrstormer said:


> Wow, um...the cyan Lux5's are really bright. Did you know they're quad-die?


Umm... yeah. All Lux5s are 2s2p quads.

"Do not look into quad-die LED with remaining eye."


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## HarryN (Dec 23, 2009)

LOL - make sure you are careful working around bright LEDs like Lux V, etc. That package is still underestimated IMHO. Make sure you keep it well heat sinked while playing - or it will die fast. Guess how I know.

There are a lot of reasons to like a particular LED package or tint. Some of it is technical, historical, and some - just how you perceive color and lighting.

One of the challenges in buying an LED, is that there is not a good separation of specs between color temperature, and spectrum content quality. I much prefer 5000 K over 3000K, even for our conventional lighting, but that does not mean I am happy with poor spectrum content. IMHO, a lot of the interest in warmer tints is not so much from color temperature, but improved spectrum content. This is masked / confused by the CRI number, rather than for me, a more useful number comparing it to sunlight. The incan guys have found the same thing, as they are constantly pushing up the bulb temps to cooler white temps by "over driving".

Back to building flashlights. I have built lights (mostly for personal and gift use) from both Cree and Lumileds LEDs. Since I started out with Lumileds, I tend to use it as a "baseline", and compare if other LED options are "substantially better" for an application. This means that the other LED does not have to be “just a little better”, but “substantially better” to be considered. This is of course different than someone starting from a "Cree" baseline and working in reverse.

Using my “baseline” as a comparison starting point:
- It is hard to beat a Lux III red / orange for output or robustness at anything close to that price point. It is now obsolete – rats.
- The Lux V is a great LED for using in 2S x Li Ion applications. I have yet to find a better LED in terms of simplicity to use in that application. Of course, it is not as bright as some other packages, but it is so easy to work with.

- The K2 is perhaps the ultimate “beater” LED. I think of it as the pick up truck of the LED world – takes tremendous abuse, and will be missed greatly. I can’ think of any similar LED package with the built in abuse resistance of this package. Of course, abuse resistance comes with a price, and that price is too high for many people, which probably drove it toward end of product life.

It certainly is a heck of a lot easier to solder these things that the surface mount parts.

- Comparing similar LED packages from Cree (single die, similar die size) - I read the Cree data sheets, and they are full of warnings about how to electrically baby their LEDs. This is not a cut on Cree parts, just an interesting point to note. I interpret this information to mean that “something” about the K2 is more electrically robust.

- Lumileds is trying hard to convert K2 users to Rebel – calling them “equal”. My perception is that that it takes about 1.5 rebels per K2 replacement (lumens), a bit disappointing, and slightly a pain, but I am attempting to see if it is viable by adding more Rebels, while also looking carefully at the MC-E instead for a build project.

- IMHO, the main advantages of the Rebel are its relatively high resistance to temperature droop, and its availability in a wide variety of colors and color temperatures. There are so many off the shelf options for color, color temp, CRI, output, etc, that it is hard to imagine that someone can’t get really close for many applications. For some applications, the high surface brightness of the Rebel will be very useful.

When you are down in the dirt designing for it, you also find out real fast why their pad layout is better than the XP-G for electrical and thermal considerations - at least that is my experience.

- The MC-E is an interesting package to me – a bit delicate, but very interesting. I have some of these for a project.

- The XP-G is a nice LED, and I bought a few for testing. It has reasonable output, but not more than an MC-E, and not that much easier optically either. I predict a shortage of this part in 2010, so I am not willing to design with it unless end user pushed.

I only buy LEDs from companies that have substantial operations in North America (merchandise trade deficit reasons) so that leaves out some other companies, but frankly, the ones I compared in the past were “also runs”, so that is not enough to get me interested vs. the potential risk. Obviously there are some specialized exceptions, like Bridgelux, LEDEngin, and Luminous, which have at least partial operations in North America


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## Neondiod (Jan 7, 2010)

How large is the die on the LUX III and the K2? If they are 1mm2, it's rather impressive they can take 1400 and 1500 mA, especeally the LUX III in the yellow - red modells.

Why didn't you get the 0220 cool white K2?


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