Cree XM-L XM-L2 led die color vs. tint

Is there any relationship between the XM led die color and tint? I mean like cool white has the die less yellow and warm white has the die more of yellow color? Is that true or is there any other simple method of determining the tint of these leds?

I have always found with XM-L or L2 dies that I can tell if the die is cool white or warm white, meaning 6500k-7000k is very light yellow and 3700k-4500k is a darker yellow, but it's not a good enough way to tell, that you could say "hey, this one is definitely 5700k" or anything like that. It's just a general rule of thumb that very light yellow dies are cooler white than very yellow dies.

There is no good way to pinpoint the color temp unless you got the info when you bought them and without expensive equipment, I don't think you could test them either.

Yes but as a general approximate rule to avoid cooler white and favour warmer white without telling 6500 or 4200K it might be OK.

If you have lights side by side you cen tell which one is cool/neutral/warm white. Cool white die is yellow, slightly pale. Warm white die is basically orange. Neutral white die is yellow but not as pale as cool white one.

Based on XP-G you can see the difference here:!

You can also see it step by step on fasttech product pictures:

As you can see there’s not much difference between two similar bins (except 1C->3B but that’s because there’s no 2x tint on FT) but the difference between cool and neutral whites is pretty clear.

That is what I expected you can tell if you have some lights/leds side by side based on the die color. Great help guys! I ordered some XM-L2 leds from FT to replace some of my XM-L lights and I like to estimate I really have cool/neutral/warm tint 8)

I know of no color reference chart or anything. Something like that would be nice to have if available. Since the phosphor layer fluoresces under UV, the die color differences exaggerate (look even more different from each other) under UV lighting.

Are there any photos available of the same tints under UV light?

A few leds illuminated with Nichia 219A 92CRI light, camera on daylight setting, on visual inspection the difference between cool and warmer leds is more clear than on a picture:

same leds illuminated with 365nm light, same camera settings, a (colour-less) 'old school' photocamera UV-filter was placed before the camera lens because the camera still picks up a bit of the 365nm (blue-ish), with the filter in place it was a bit less:

same leds illuminated with 400nm light, same camera settings again, photo was taken through (light) yellow glasses to get rid of the purple light, so the colour in the picture is more yellow than in real:

Thank you! Another interesting information I get here on BLF :slight_smile:

Those pictures are amazing!

Thank you Bort, I like them too, even apart from what they show, the colours are nice :-)

Seems like Under UV,the cooler tints glow less,and that's more significant than the yellow/orange tint.Still lots of stuff to ponder,Kelvin,tints,CRI,screen reproduction .

The whole thread is very interesting for me. Thank you guys for sharing the knowledge :wink: