Luxeon comparison chart / pics

[erv]

Hi ! I've looked over the forum, I don't think this has been posted before, but maybe this topic could be moved into the LED Q&A section, if necessary.
I decided to take some pics of luxeon LED at different currents, same blade (double wrap diffusion film + light guide film) and holder (my last anakin custom machined blade mount). I'm using my new board Crystal Focus powered by a lab power supply at 5.2 V (equivalent to 4 AA nimh still warm from a fast charge). Blade is 91.5 cm long total, 6.5 cm hidden in the blade mount.
I took to sets of pictures, in a dark room, then in a normally lit room (daylight coming thru the window). To be able to see some slight differences, a "-2" exposure was applied to the digital camera, fixed ISO speed (400). Background is a bit darker than actually seen but the blade brightness and color is pretty accurate to what you see in person. The lux 3 and K2 obviously don't have the same wavelength even if pretty close. You can see a difference of brightness by looking a the section of the blade which is supposed to be dimmed (at 4/5th of the blade length). Between 700 mA and 1A on the lux III, there is obviously a better brightness when looking a the background, not the blade : light is radiating further from the blade. Less obvious for the K2, confirming what I see by my eye, it's pretty difficult to see a difference between 1A and 1.3 A, except that whe you vary the current by hand, you notice a little difference. For the K2, the difference is noticable by looking at the 4/5 th section of the blade, slightly more white and saturated at 1.3 A.

http://www.plecterlabs.com/Media/BladeComparisonDarkRoom.jpg
http://www.plecterlabs.com/Media/BladeComparisonNormalRoom.jpg

[MasterStoney]

wow that k2 looks a lot less brighter than the lux III

[vortextwist]

that was pretty much what I thought, the second pic looks more evenly lit than the others. Maybe it's just the pics but they seem to be pretty good pics.

[erv]

yep, that's what I wanted to highlight, despite I have a low experience with K2. I can say that this one is however brighter than the model I put in my obiwan saber (I'll soon upgrade it). This ref is a LXK2-PB14-N00 while the one on my obi is LXK2-PB12-K00. The advantage of the K2 is to give more lumen per watt, hence less heat at equivalent brightness, and theoritically can go brighter than a lux III, but only on certain colors, blue included. Since this is one of the less bright colors, I wanted to picture the comparison on blue.
I think I'll stick to lux III for a while. Maybe lux V if I can find a good source of li ion batteries in europe. Lux V is really brighter, but I have to make pics as well.

[xwingband]

Yeah, sometimes the benifits are marginal. I know my K2 green is better than my Lux III green.

But at least it shows the difference. Personally I'd drive it harder. It does seem more evenly lit on both.

[erv]

Yep, since the K2 is supposed to be brighter for some colors, I think it can be seen somehow, I'm still puzzled about the way my camera pictures this. Again, those comparison pics are not... how to say... some thuth by them self. Especially because the lux III and K2 don't have the same wavelength. What can be seen anyway (and that's the most important IMO) is that when you add some more current, you get a benefit :D
Erv'

[Novastar]

Hi Erv... looking forward to receiving my Crystal Core (yay, he's shipping it soon... I'm as giddy as a bloody school boy)...

Anyhow... remember the following when taking photos:

1. Every camera is different, and will display its own "distortion/bias" on certain wavelengths but not on others.

2. Whatever the case, ambient light IS present and also figures in no matter what. Flourescent, "true" white light, "warm" white... it all matters.

3. As you know Erv, shutter speed makes a lot of weird differences from shot to shot, camera to camera.

4. As you mentioned Erv, actual LED wavelength differences. Even two Lux Cyans right next to one another... are unlikely to be the same bin.

5. Computer screens! Everyone is looking with a different screen which ALSO has its biases in how an image is displayed. Sounds like nitpicking, but it's very true!

6. Lens size. Imagine using a "super professional" camera over some consumer one. A pro-sumer cam over that one, etc. etc. This affects the light the camera is able to "capture" so-to-speak.

The list goes on, but you get the point.

All in all... there really is NO standard when people are posting photos. Only among the same sabers in the same shot with the same camera... but even then, there are so many factors that "muddy it up" when people are trying to make distinctions that are tiny. Such as 10% darker or brighter. That is NOTHING.

A saber that is 50% brighter or more than another... now THAT is something that is undeniable. That will come in time...

[neophyl]

Have a look here http://www.lumileds.com/products/line.cfm?lineId=18

That N00 K2 led is only rated for an average of 21 lm. A Q00 is 35lm so a little better than a normal 3w.

A LB3C blue 3w is rated for 30 lm. So your K2 blue isnt supposed to be brighter.

You have to be carefull with the ordering codes and making sure you are getting the highest ratings.

[erv]

phil is right ! My first order was only a N00 cause the retailler only had that model at that time. Then after I got a Q00 which seems better for true, even if I don't have an "absolute eye" for brightness measurement.

[Novastar]

Not only are the ordering codes important, but the differences in the ma you're running.

Since some of the K2s list "X" lumens at 1500ma... you can't compare a Lux III of the same "X" lumens at 1000ma...

...since if you're running a board that spits out 1A (such as Corbin's)... the K2 may not be brighter, it may be WORSE.

Then again, if you do the calculations and are only interested in the top ma (such as 1500ma) and running your LED... well, the K2s have it.

But Erv's current CFv1 only functions up to 1.3A... so expect a K2 rated at 130 lumens to run more like 86% of that... 112 or whatever.

That is also exactly what Erv told me in an e-mail.

Wow, I'm REALLY learning I think! THANKS PHIL, THANKS ERV.

My God, I'm a huge nerd. Crud. :shock:

[neophyl]

I like manufacturer datasheets that list output at the common various currents or at least have a graph of lumen vs current. That way you can compare different leds at the same current values to get a better understanding of what they are doing.

EE isnt just about designing circuitry, theres also boatloads of reading up and learning how to interpret the data that manufacturers do give you. Some of them are quite sneaky in the way they present it. Bit like governments and thier statistics ;)

Cant wait for my Seoul P4 to arrive. I REALLY want to test that baby. Ive got a toast running one of the U00 white K2's at the moment so about 100 lumens which is pretty bright. The P4 is rated to put out 100 lm at 350ma, and 240lm at 1000ma.

[Novastar]

Sounds great Phil! I'll have to look into that--I don't know much about LEDs other than the Luxeons these days, and most everything ELSE I see is just not as bright, too big, too much voltage requirement, or just about equal to Luxeon.

I agree that a lot of data comes into play for being an EE... even though I'm NOT one of them! :) Everything I learned came from a mixture of starting BOP I (where I knew NOTHING, and spent a lot of time listening to Corbin), wiring a few things up myself by trial & error, and then staying updated on forums/threads.

Hope to see you at C4...