de-doming: illustrations for color changes and increased luminance

I tried dedoming a whole bunch of XML2s. The only one that didn’t look green was the 3A tint. 3A looked by far the best.

I was not too pleased with my XM-L2 3A that I de-domed. Only did one though.

There is also some randomness when it comes to de-doming and tints. So If you de-dome 10 emitters, you are more likely to get one or some with a not so bad tint.

Great article!

Thanks for posting this data and analysis sma. Great work.

wow. this is really really good.
Didnt know squeezing dome flat is an option!

Do you think you could test the XML2 U2/1A and XPG2 S2/2B? Since these are the highest output for now?

amazing work man

I’m looking for an XM-L2 to dedome that would compliment an MT-G2.

Amazing test. If this is the quality of your posts, I'm going to have to check out your other 4 posts. I'd love to know how you did the first test. I was looking at some sensors on Sparkfun a couple days ago and thought they might be able to create results like this, which is more incentive to start playing with Arduino.

Thanks guys for your positive reactions!

I held the sensor directly towards the LED at a distance of about half a meter, but distance is not critical. I had to pay attention not to twist it at all as the results were drifting then, perhaps due to some effects in the perforated plastic grid front of the very sensor. The sensor gets along fine with the illuminance, even at very high amps. It has problems though with the much higher illuminance if you point at it with a flashlight (that is, LED with reflector or lens), unsurprisingly. More distance, or a good gray card and indirect illumination is required then.

Difficult, especially if the actual chroma coordinate of your LED is at the upper end of "2C".

It might be important that 1A is much cooler and the shift is more high-angle than for 2C.

Best conditions: It's both below the black body curve and relatively warm (that is, low angle and shorter shift).

By the way, while doing the above tests I searched the forums (most results here in BLF) and found positive reactions about all 4C/D, 3A/C, also negative reactions about 3C (surely both a matter of taste and the variation within one bin), as well as negative about all 1* and 2*, and 2B/C, 3B.

I would be happy to test them all if you send them to me :) (should mention that this means germany). I'd send them back to you at my own cost, for reasons of curiosity. However, both color bins don't seem to be "promising"...

I have not dedomed all that many xml but found that the warmish purplish ones responded best to my eyes.
good job!

Very nice work, thanks a lot for doing these tests! And well represented, thanks for that too :-)

Picturing colour checker cards is difficult I found, you loose a lot of colour information that was there in reality.

I've got an XP-E2 R4 1C that I installed in a reflector with a pinhole type opening. The tint is really green. Is it possible that the dome got cracked or damaged at the base to produce such an ugly tint?

The tint is not as green in real life as in the photo, but it's pretty ugly.

I ordered red another XP-E2 R4 1C just to find out if this emitter is damaged or flawed. It's just makes me feel like it's been dedomed with the dome still on.

could have gotten overheated too.
had an xml that got run hot enough to solder short shift to the greenish side a bit.didnt seem to hurt it otherwise.

Great work sma. Definitely sticky worthy.

So what is the cause of the tint shift? Does the silicone absorb certain colors? Why do the cooler tints shift more? Does anyone know yet?

DrJones has made a fine lecture on this subject :-) :

Thanks djozz. Read that way back when, but missed or didn't understand this paragraph at the time (from linked thread in djozz's above post):

"Another observation can be explained by this: XM-Ls have quite some angular tint shift, i.e. the light emitted to the side is substantially more yellowish, while with the dedomed LED this effect is greatly reduced. The YAG phosphor has a refractive index of about 1.8. the critical angle agains the dome (~1.5) is about 55°, which means that such a ray to the very side has traveled a 74% longer distance through the phosphor compared to a perpendicular ray and more blue photons get converted to yellow. Without the dome, the critical angle against air is 33°, resulting in only 19% longer distance in the phosphor and thus much less angular tint shift. See these nice images by Tecmo: (post #431)"

Apart from being injured by overheating as abovementioned, it might perhaps just be an LED from the upper "green end" of the 1C area?
I really believe you would see mechanical damage with a magnifier or even the naked eye.

Indeed. I guess, strictly speaking they should only be used with a calibrated chain (camera, software, graphics card+monitor).

Absolutely! It both covers tint shift and increased luminance. That's why I also had linked it at the very beginning of my post:)

His post was the first time I learnt the real explanation, instead of the idea "same lumens from smaller area".

Yep, same with me, and even after reading it it took quite some more thinking to really understand what is going on optically.

I’ve also read his post several times. Even if we set all of his other work aside, that one post is and has been a huge asset to us!

Like ImA4Wheelr, I don’t think I really absorbed the tint shifting business DrJones presented until looking at it this most recent time (which was after reading SMA’s great post showing where the rubber meets the road!).

That’s not surprising. You are using a colorimeter - it can’t really do the measurements you want. It makes certain assumptions about the spectral distribution of the light source, that are not necessarily true for the LEDs you are measuring.

I happen to have a real spectrometer (Spectrocam) and a colorimeter (i1 Display 2). E.g. for my TK35 (XML T6), the i1 measurement is about 500K too cold and a bit too green. Your Spyder has very different color filters/tuning compared to the i1, so errors will be different.

That being said, I think your measurements are useful as an qualitative indication of the color shift. But the actual amount will probably be wrong, since the spectrum of the LED will likely change a fair amount…