# cree vs luxeon



## Axkiker (Feb 2, 2009)

So just today i recieved my first set of blue cree emitters.... I immediatly opened the package and pulled one of these little suckers out and hooked it up to my powersupply

My first reaction was "this sucks". I really dont see them being any brighter than the luxeon emitters I was buying. These crees are supposed to put out at least 30lm at 350 ma. The luxeon were supposed to put out 30 lm at 700ma. So I naturally thought at 700ma the cree would blow the luxeon away. not so much. I havent had a chance to set them up side by side. I plan on doing that tonight. I dont expect much of a difference though.

My next thoughts are a little better. The cree didnt seem to get nearly as hot as the luxeon. This is a great advantage to me.

have you all had the same experience with the crees not getting as hot. If for no other reason the heat issue may be a reason to keep using the crees. However if not then back to the luxeon I go. The luxeon are cheaper and easier to get.

any thoughts.


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## Gryloc (Feb 2, 2009)

Well, first of all, the Cree is operating at a lower power (more than half as much), so that is why they are running cooler. Secondly, are you attaching the emitter or star to the proper heatsink? What are you using to power up the emitters? How can you be sure they are getting the exact current? If you have a constant current power supply, you could always hook them in series and power them at both 350mA then at 700mA to see how they compare side by side. 

Where did you purchase your blue Cree? How can you be sure if it is the 40lm binned blue? Few places offer the higher efficiency blue emitters. I think DX sells the X-Lamp blue emitter, but it uses older technology (which is equivalent to Lumiled's luxeons in therms of efficiency). Cutter may sell the 40lm blue emitter, as well as LED Lighting Supply. I am interested in hearing more about these...

-Tony


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## HarryN (Feb 2, 2009)

I think your initial observation is closer than you think. Cree and Lumileds are at technologically similar points in time - there is not a 2 X difference between their products in real life / use.

It is important of course to mount them all for proper heat sinking, even those tiny little rebels with their anti - droop technology. (reduced temperature sensitivity.)

BTW - blue is the most dim of all visually, and you really need a large change to notice the difference.


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## Axkiker (Feb 2, 2009)

Gryloc said:


> Well, first of all, the Cree is operating at a lower power (more than half as much), so that is why they are running cooler. Secondly, are you attaching the emitter or star to the proper heatsink? What are you using to power up the emitters? How can you be sure they are getting the exact current? If you have a constant current power supply, you could always hook them in series and power them at both 350mA then at 700mA to see how they compare side by side.
> 
> Where did you purchase your blue Cree? How can you be sure if it is the 40lm binned blue? Few places offer the higher efficiency blue emitters. I think DX sells the X-Lamp blue emitter, but it uses older technology (which is equivalent to Lumiled's luxeons in therms of efficiency). Cutter may sell the 40lm blue emitter, as well as LED Lighting Supply. I am interested in hearing more about these...
> 
> -Tony


 

Well I was running the cree at 700ma... I have been using a large piece of aluminum with paste as a heat sink. So im not sure what the difference in heat is yet. Im going to do exactly what you said and hook them up in series side by side to see what difference there is if any...

I purcahsed my cree's from led supply. I was very specific when I ordered them. I got on the cree website and looked up the tech bulletins and made sure I ordered the 30lm at 350ma emitters. Now who knows if thats what I got but its what i ordered....

I havent had a great deal of time to screw with them so once I do ill report back and let you know what I find


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## Fallingwater (Feb 2, 2009)

HarryN said:


> BTW - blue is the most dim of all visually


Nope - red is.


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## Gunner12 (Feb 2, 2009)

HarryN said:


> ... even those tiny little rebels with their anti - droop technology. (reduced temperature sensitivity.)...


I don't think that those are used with the rebels or any production LED, but I could be wrong.

Yes, red should be the least visible per watt of light.

IIRC it takes 4x the light for a source to seem 2x brighter, not sure if those numbers are correct(or work for blue light) but it does take a lot more light for one source to seem 2x as bright as another. So you might not see a huge change in output when there actually is a decently large gape between the outputs.


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## HarryN (Feb 3, 2009)

Ok, I guess I answered a bit fast in my attempt to help. 

When I think red (650ish nm ) I tend to actually think of red / orange ( 617ish nm). These R/O LEDs are quite efficient per watt and easy to see (used as red lights)

Blue emitters (460 ish nm) on a per watt basis have fairly low visibility by comparison, at least to my eyes.

The main point is that you will likely not be satisfied if you expect that the LEDs from one market leader will be dramatically better than similar LEDs from another market leader. This would be similar to expecting a Ford pickup truck to be 2 x as fuel efficient and 2 x as fast as a similar Chevy.

I suppose next, someone will say that Cree is 10 years ahead of everyone else and that their ____ doesn't stink either. :shrug:


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## Oznog (Feb 3, 2009)

Well it depends on whether you're talking about photopic (daytime) or scotopic (low-light adapted) vision.

http://en.wikipedia.org/wiki/Photopic_vision
http://en.wikipedia.org/wiki/Scotopic_vision

AFAIK that is scaled as visible response per mW of light energy. Note this is not per lumen, that would be recursive nonsense. Lumens are a unit of visibility, already adjusted as per the _photopic_ scale. 

All said, 50 lumens of blue should be perceived as "similar" to 50 lumens of green or 50 lumens red in photopic conditions. During scotopic conditions, the reaction to red drops way down though and 50 lumens of red may appear "weaker" than 50 lumens of green. 

What the photopic chart tells us is that far more mW of light energy is needed to make 50 lumens of blue than 50 lumens of green. When an LED mfg tells us it's 80 lumens/W for the greens and 40 lumens/W for the reds, that's not necessarily saying the greens are more efficient in terms of mW of light power out since the mW out have been highly biased for the green ones.

Unless you have equipment to measure or place 2 LEDs side-by-side for comparison, brightness estimates are next to useless. For one, the human eye response is inverse-exponential. If you show someone light source A and ask him to pick what seems "twice as bright" from another light source by his judgement, he'll pick one with 4x the lumen output not 2x. In fact some of us have a hard time noticing 350mA vs 700mA outputs even though the light meter reports a 75% power difference.

And that's totally blown away by the human eye adaptation to ambient conditions. What seems like retina-burning in the dark may seem "normal" in indoor lighting and not even visible in direct sunlight. With judgement this inconsistent you just can't quantify the source this way, not within like +/- 50% unless you're an especially well trained eye.


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## Axkiker (Feb 3, 2009)

Well here is my first impression of my new blue cree leds compaired to my blue luxeons

Well the first test was actually soldering them to the thin flexible pcbs I make.

The cree is by far harder to reflow. The cree has those little pads on each side of the bottom which you need to solder to the board. Well I was able to do it however it just seems like a PITA. You have to position them just so so in order to make sure you dont short the little bugger out with the thermal pad on the bottem. The luxeons have those little leads sticking out each side which you can easily apply paste to and them reflow. Now this was my first shot at reflow soldering so maybe im doing something wrong. I just find trying to set them exactly in place so only the very ends get solder is a pain.

The next test was burning them side by side in series. I supplied 700ma with my power supply and I can see a difference with the cree. It is fairly brighter. I cant say its a huge difference but with blue every bit helps.

The biggest thing that I have found is that the cree runs much cooler. I cant give you an actual temp as I am only checking by feel. I however am positive that the cree is running cooler. 

Im gonna keep experimenting with them just to see if either or has any major advaltage or disadvantage. As of now the only thing I dont like about the cree is trying to reflow them.


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## spencer (Feb 3, 2009)

The Cree is more efficient. That is why it runs cooler. It uses less power for the same amount of output. That is a huge advantage for it.


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## Oznog (Feb 3, 2009)

What Cree and what Luxeon are we comparing?

Efficiency makes very little difference in heat generation. IIRC these can be something on the order of 20% efficient. So a vastly more efficient emitter might generate like 700mW of heat instead of 800mW. 

Heat at the front has far more to do with the thermal conductivity of the board (and the LED power level) than the LED efficiency.

Reflow is cake. Solder paste, tweezers, heat gun with a temp-control dial standing on end.
Slowly lower the device closer to the heat gun, with the air heating the back. You want to first observe the flux boiling out. Once you see this start, back off a bit and wait like 10 sec for it to finish. Then finish lowering it until you see the solder melt, hold for a few sec, then pull it out of the stream. You really can't screw this up, the solder self-positions the device(s). Just don't overheat them and burn up the MCPCB insulator. 

Or just use a hot plate, whatever.


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## asdalton (Feb 3, 2009)

spencer said:


> The Cree is more efficient. That is why it runs cooler. It uses less power for the same amount of output. That is a huge advantage for it.



But he said that the Cree was running cooler at the same drive current, not at the same light output.

If so, one reason is likely that the Cree LED is putting more of its energy into the radiated light rather than into heat that has to be conducted away. 

It is also possible that the Cree has a lower Vf, which would lead to less power consumption at the same current. This would be easy to check with a voltage meter while the LEDs are running.


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## HarryN (Feb 4, 2009)

It would be helpful to know if this is a Lumileds K2 or Lux V or rebel - I assume a K2 ? Which Cree model ?

Perhaps for all of us curious people, you can show a picture of the setup ? :thinking:


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## 2xTrinity (Feb 4, 2009)

> BTW - blue is the most dim of all visually





Fallingwater said:


> Nope - red is.



You're both wrong -- IR, and UV are tied for the most dim visually/ watt output power. Sensitivity "peaks" in the green, and falls off in BOTH directions.



> What the photopic chart tells us is that far more mW of light energy is needed to make 50 lumens of blue than 50 lumens of green. When an LED mfg tells us it's 80 lumens/W for the greens and 40 lumens/W for the reds, that's not necessarily saying the greens are more efficient in terms of mW of light power out since the mW out have been highly biased for the green ones.


As far as light power out / electricity in is concerned, green emitters are the _least_ efficient of the visible-color LEDs.

Green at ~530nm has a theoretical ceiling of 600 lumens/watt. Real devices are cranking out 60-80, corresponding to about 10% power efficiency. Blue and red LEDs conversely have been made to approach 40% power efficiency. That is why a blue LED with a lossy phosphor coating on it (eg a white LED) can _still_ cranking out more lumens than a green LED at the same power.

White phosphor LEDs are able to top 100lm/watt because of the insanely high efficiency of the blue dice compared to the other colors. RGB on the other hand will top out at more like 50-60 (if you consider the "best" blues, greens, and reds get 30/80/40 lm/W respectively) 




> My first reaction was "this sucks". I really dont see them being any brighter than the luxeon emitters I was buying. These crees are supposed to put out at least 30lm at 350 ma. The luxeon were supposed to put out 30 lm at 700ma. So I naturally thought at 700ma the cree would blow the luxeon away. not so much. I havent had a chance to set them up side by side. I plan on doing that tonight. I dont expect much of a difference though.


In order to judge the relative brightnesses, you should run the LEDs at close to the same power as each other, and do A-B testing with ceiling bounce. Your eyes will be able to tell the difference between light that is uniformly spread out, than light in a bright "point" (as a point source of just about any brightness will cause pupil constriction and saturation of the retina)


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## lyyyghtmaster (Feb 4, 2009)

Yes, ceiling bounce will definitely prove more accurate. Also the lottery applies here. Blues are of all different wavelengths typically, sometimes even in the same batch, and shorter wavelength blues will appear slightly dimmer at the same mW output. Try adjusting distance from a white target to each LED so their brightness is equivalent and see if one appears to be deeper blue than the other. It might help to include various light-colored fluorescent and non-fluorescent items in the "target space".

BTW I have noticed that Luxeon whites use a slightly deeper to equivalent blue die to that typically used in Crees, but Seoul SSC often seems to use a somewhat shallower blue, thereby possibly explaining the slight edge in luminous efficacy they (used to?) have.


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## yellow (Feb 4, 2009)

so, hooked in series, running on the same current, the Cree is brighter and runs cooler than the Luxeon...
... what is the problem then? Its totally correct.


(but I thought - with colored led - there is not much difference and the old Luxes still are good) :thinking:


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## Fallingwater (Feb 4, 2009)

2xTrinity said:


> You're both wrong -- IR, and UV are tied for the most dim visually/ watt output power. Sensitivity "peaks" in the green, and falls off in BOTH directions.


Technically yes, but we're talking about LEDs useful for intense visible light here.


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## ledstein (Feb 4, 2009)

I was lucky enough to play with all power leds from all the "big names": " Cree, Lumileds, Seoul, Osram". 
My important advice for you is simple: forget the numbers, just test the leds. Lumens are for leds as mhz where for cpu´s: pure marketing with the big difference that you actually can´t test the numbers yourself or be sure from what bin the leds are.

More to the point: Cree leds should be the best right now because of one simple reason, they are designed to run at lower current (350mA). At 700mA and beyond heat becomes a big issue and few producers are willing to implement oversized heatsinks in their products. No one will use high currents in real life nomatter what the producers say about the performance at those levels. 
For DIY my advice is to use only star versions and ALWAYS use a constant current powersupply.


ps: If you care about the numbers i found this website where you can compare all the brands/types of power leds :
http://www.ledrise.com/index.php?cat=c2_High-Power-LEDs.html&language=en


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## HarryN (Feb 4, 2009)

ledstein said:


> I was lucky enough to play with all power leds from all the "big names": " Cree, Lumileds, Seoul, Osram".
> My important advice for you is simple: forget the numbers, just test the leds. Lumens are for leds as mhz where for cpu´s: pure marketing with the big difference that you actually can´t test the numbers yourself or be sure from what bin the leds are.
> 
> More to the point: Cree leds should be the best right now because of one simple reason, they are designed to run at lower current (350mA).
> ...



I am having a hard time agreeing with this information.

a) Designed for 350 vs 700
- Normally, an LED designed for 700ma operation will be more efficient at 350m.
- I may be entirely wrong, and one die may be different than the other technically, but this is not the reason IMHO.

b) Part Type
- So far, we still have no idea which LED package(s) the poster has used or how well the heat removal really is.
- For us to speculate on the results without this info is not useful.
- It is difficult to take the results seriously - we don't even know if it is a single die vs multi die package being compared.

c) Binning vs Marketing
- While your general concept might have some merit, that binning is a factor in marketing, it is not "just marketing"
- While it is quite difficult to stand around and shine an LED on the wall and exactly tell the bin, I know plenty of people that can easily identify which "similar" LED is brighter, has a nicer beam, and has a more pleasant color "for their eyes".
- I suggest you take the time to build or buy a few flashlights and go for a walk through the woods, or try cooking a steak by the light of an LED flashlight before you decide that color temperature and binning are not useful and significant.

d) The web link
- Surely you do not believe the numbers from an on-line retailer as your main source of information about LEDs ?

e) Lumens per die
- The "typical" results today from the major producers are all in the range of 100 Lumens per 1 x 1 mm die for similar packages and white color temps.
- After that, it is a matter of binning, packaging, and marketing.
- I will admit that some suppliers are more active in promoting their products on internet forums than others through stealth memberships.


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## Oznog (Feb 4, 2009)

HarryN said:


> I am having a hard time agreeing with this information.
> 
> a) Designed for 350 vs 700
> - Normally, an LED designed for 700ma operation will be more efficient at 350m.
> - I may be entirely wrong, and one die may be different than the other technically, but this is not the reason IMHO.



Generally you'll find these devices' power ratings has a linear relationship with the package's thermal resistance. The thermal resistance of the package often presents more of a limit on the maximum power than any other factor.


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## ledstein (Feb 5, 2009)

HarryN said:


> I am having a hard time agreeing with this information.
> 
> a) Designed for 350 vs 700
> - Normally, an LED designed for 700ma operation will be more efficient at 350m.
> - I may be entirely wrong, and one die may be different than the other technically, but this is not the reason IMHO.



I didnt want to go into details but it seems i should. Also i will stick with white color because i have much more experience with white.
Luxeon K2 TTFC LXK2-PWC4-0200 (ignore the recall problem, just focus on the numbers) is marketed at with [email protected] (Min) and [email protected] (Typ). If you dig in the datasheet you also find the flux at 350mA which is 95lm.
Cree X-RE Q5 is marketed with [email protected] (Min). 

So i say again, the best led is the one the has the highest flux at the lowest current (if the voltage is the same). Its better because of the heat issue.




HarryN said:


> Ic) Binning vs Marketing
> - While your general concept might have some merit, that binning is a factor in marketing, it is not "just marketing"
> - While it is quite difficult to stand around and shine an LED on the wall and exactly tell the bin, I know plenty of people that can easily identify which "similar" LED is brighter, has a nicer beam, and has a more pleasant color "for their eyes".
> - I suggest you take the time to build or buy a few flashlights and go for a walk through the woods, or try cooking a steak by the light of an LED flashlight before you decide that color temperature and binning are not useful and significant.



Binning is more about the problems with the way the leds are produced then its with marketing. The same problem have cpus. Ofcourse u need to know the bin of the each led you compare.



HarryN said:


> d) The web link
> - Surely you do not believe the numbers from an on-line retailer as your main source of information about LEDs ?



Actually i take all the numbers with a grain of salt. First because the industry doesnt have (yet) standards for measuring led performance. Second it seems to me that all the big producers try to confuse you with their datasheets. Some give the numbers as typical values, others minium, others maximum. 
Third, is no use comparing two leds based on their luminous flux if the current at which was obtained is not the same.

And forth, considering online shops are the most used way to get our hands on leds there must be a degree of trust in what they say. Otherwise where can you buy them from? No official distributor will look at a small customer.



HarryN said:


> e) Lumens per die
> - The "typical" results today from the major producers are all in the range of 100 Lumens per 1 x 1 mm die for similar packages and white color temps.
> - After that, it is a matter of binning, packaging, and marketing.
> - I will admit that some suppliers are more active in promoting their products on internet forums than others through stealth memberships.



Actually i admit that considering the lack of standards and the fact that buying leds in small qtys is sort of a lottery any brand name will do. Its more a factor of brand awarness then its performance.


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## Axkiker (Feb 5, 2009)

WOW you all sure know way more than I thought anyone could ever know about leds. 

My goal here is to find the brightest possible blue led. Reason being is this is for an under water project where water conditions can be murkey. So weak blue leds suck.... As we know blue is a pain when it comes to light output and I just cant double the amount of leds used due to size constraints etc... Im also in the process of experimenting with lenses etc.

so let me answer a few questions others above have asked.

The cree led used was XREBLU-L1-0000-00K01
30.6 min lux at 350 ma. I was very specific as to needing these leds so hopefully its what I got.

The other led which I used was one of the lumi leds which I purchased off ebay. They are the 3W version and who knows what the exact output is because it seems all the fools on ebay lie.

Each of the leds were soldered to a thin flexible pcb in series... I added a couple extra leads so I could run them individually as well as in series.

The pcb was then attached to a piece of .125 thick aluminum which was roughly 3"x3". I added a blob of heat paste on the bottem to promote heat dissipation.

The first test was running them in series at 700ma. From a visual inspection the cree seemed to be brighter. Not by a great deal but still brighter.

I then ran them individually for several minutes to see if either or produced more heat. The cree was running significantly cooler.. Or at least thats what I gathered by feeling the heat sink. I dont have an IR thermometer so I cant give an exact reading.

anyways hope that clears up everything... Or at least makes it as clear as mudd.


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## ledstein (Feb 5, 2009)

That blue cree LED is from the brightest bin.
From Luxeon there is LXK2-PB14-Q00 which can go "up" to 35lm at 1A.
It seems Osram Platinum DRAGON has also 35lm.
Seoul P4 blue has 22lm.

Maybe "silly" question. Why dont you use cyan leds? Luxen K2 Cyan LEDs have up to [email protected]


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## Axkiker (Feb 5, 2009)

ledstein said:


> That blue cree LED is from the brightest bin.
> From Luxeon there is LXK2-PB14-Q00 which can go "up" to 35lm at 1A.
> It seems Osram Platinum DRAGON has also 35lm.
> Seoul P4 blue has 22lm.
> ...


 
Yeah thats the reason I was specific to order from that bin. I need the highest output possible.... I figure if its pushing out 30lm at 350 ma I should be somewhere around 50lm at 700ma.... Or somewhere close anyway.

I am pretty new to this whole LED deal...... I havent messed with the cyan leds but am considering ordering a couple just to see what they look like.

The blue is only for astetics so im not sure how close in color cyan is to blue. If its close it would probably work out. Or at least be another option.


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## Axkiker (Feb 5, 2009)

ya know after thinking a little I thought I would ask. How close to blue is cyan..... 

anyone out there experiment with both. Im curious how much of a difference there is. From my understanding the cyan is more of a greenish color....

any thoughts.


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## SemiMan (Feb 5, 2009)

Even the ceiling bounce test will not necessarily be accurate, but it will be much better than looking at the LEDs. Cree is a 70 degree emitter, the Luxeon is 120degrees. That is a huge hugh difference in candela when looking right at it.

It sounds like you have older Luxeon as well.

That said, Cree does have superior blue right now... perhaps 20% better at the top end.

Luxeon if older will be running hotter in all likelihood, it will likely be about 20% hotter from a higher typical forward voltage of the older Luxeons.

Cyan is very green.... think some of the green approaching blueish traffic lights (the green in many is actually Cyan).

That said, bright blues are often at a higher wavelength.

Semiman


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## ledstein (Feb 6, 2009)

I think you should try cyan if your choice for the type of blue is more based on taste. The answer to your question is too subjective.


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## lyyyghtmaster (Feb 6, 2009)

I agree cyan is pretty greenish. IIRC they are nominally 505 nanometers, but ordering cyan Luxeons, I have gotten ones between about 490 and 510nm.

With Lumileds at least, playing the lottery sometimes resulted in blue Luxeons of 480-485nm. This color is visually bright, to me calming and peaceful, and yet reads as blue. It is a light aqua blue with just the faintest hint of green at 350mA. Think ceramic blue C 9-1/4 Christmas lights.

It often takes a fair number of separate purchases spread out over time/LED package types to get the exact color you want, and then if you do get that rare color, you re-order immediately and still aren't assured of getting the same bin with your new order. I've gotten Luxeon blues between about 460 and 485nm.

I don't know if these observations are true of the Cree blues as well. Do they ship a wide range of blues, or are they all right around the typical 465-470nm medium blue <rant>that everyone thinks everyone always wants?   :thinking:</rant>

Regarding royal blue, I think the Crees don't go quite as deep as Luxeons. Cree is only binned down to 450nm, while I've gotten Luxeons/Rebels between 440 and 460nm. The deeper versions of this color are starting to get fairly dim, but boy oh boy is that a striking blue! I've had numerous people (not flashaholics) ask me if it's blacklight!


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## ledstein (Feb 6, 2009)

Well there is another important aspect. Lumileds offers also star versions directly unlike cree leds which are made into stars by 3rd praties. On the back of each original star luxeon there is the exact bin including a number thats shows the wavelenght interval.For cyan bin code 1 is 490-495nm and 2 495-500nm.

Luxeon k2 star leds come in packs of 56 and usually all are o the same bin. Its really not hard for a online led shop person to take a look in their stock and see the bin especially for a few leds. Just call them or email and ask in a convincing manner for a 1 or 2 bin. Or u can just ask what bins they have.


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## deusexaethera (Feb 6, 2009)

For what it's worth, I was recently upgrading my father's collection of Mag-Lites to use LEDs, and I experimented with a few different configurations: one was a cheap 3xLED with a cylindrical reflector, the next was a 1W Luxeon LED with built-in regulator, and the last was a 5W Cree Q-something LED with built-in regulator. Obviously the 3xLED setup couldn't compete, but I was surprised to find that the 5W Cree LED wasn't any brighter than the 1W Luxeon was, and the Luxeon produced more yellow light to boot.

Now, preference of light color is a personal thing I guess -- some people like the dazzling effect of blue-white light and others don't -- but the human eye is designed to see using yellow light, while blue light is only useful for establishing color balance. That's probably why I thought the 1W Luxeon was just as bright as the 5W Cree, because the yellow content of the light was probably pretty close to equal.

Given that, the Luxeon is probably the better choice unless you really need snow-white light.


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## asdalton (Feb 7, 2009)

There's no way that a Luxeon emitter will be equal in output to a Q-bin Cree emitter at the same drive current. Not even close. Tint is irrelevant here, because the Cree is greatly superior.

But the stock Mag reflector is a poor choice for the Cree emitter, because the Cree's angle of emitted light is too narrow, and the reflector will catch only a small fraction of the light. You won't get a strong beam with this setup.


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## Axkiker (Feb 7, 2009)

well guys I have been stressing with these blue leds. Constantly trying to figure out which blue was gonna give me the best results.

I picked up a small piece of blue translucent plex the other day and have been messing with that. I have been putting white leds behind it and have been getting great results.

So Im thinking I may be just as well off to use a few extremly bright white leds and use the blue plex to produce the blue lightinsted of blue leds

Even though the blue plex will reduce the light output. I think by switching to a superior white led will compensate. I kinda think it may even give a brighter blue. Maybe not as true of a blue color as a true blue led however that doesnt matter in this application.

anyways ill let you know when I do some testing.


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## blasterman (Feb 7, 2009)

If you use a blue filter in front of a 'super-white' emitter, like a Cree R2, you'll likely get a much brighter blue simply because the bandwidth of the filter is much wider.

In some respects this is an advantage because mixing deep blue with just a bit of red, as per some Rosco gels, produces a more aethestically pleasing color even though the LED is producing a more pure blue. I've been trying to get blue LEDs to match the blue-blue-violet look of blue colored CFLs, and haven't been able to do so for such a reason.

However, filters will eventually have to be replaced.

As per my other posts to you on the topic, I suggest trying the 3-watt blue ProLights from BestHongKong. The are significantly brighter than my blue Lux III's, and they are cheaper.


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## lyyyghtmaster (Feb 9, 2009)

blasterman said:


> I've been trying to get blue LEDs to match the blue-blue-violet look of blue colored CFLs, and haven't been able to do so for such a reason.



CFLs have a strong peak in the blue/violet wavelength of 435nm. The deepest blue power LEDs I have found (Luxeon/Rebel royal blue wavelength bin 3) bottom out at 440nm and most are not even this deep. The non- royal blue are shallower still. Try getting 3-bin royal blue Rebels, they look pretty violetish. Then mix in some regular blue and a small amount of cyan. That will get you pretty close to a blue CFL.


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