Tint, Binning, and CRI Explained (For XM-L LEDs)

I figured I'd make a guide related to XM-Ls and tint, binning, CRI, and all the other details I can think of. :)
There are 3 basic tints.
Cool White is a very pure white and is what most lights are. This generally has a low CRI (color rendition index) and will not show colors that well. Some people say that it is to blue. It is generally around 6000k.
Neutral White is considered to be one of the better tints as it still seems fairly white, but does have a higher CRI. It tends however to be slightly tan colored rather than a pure white. It is generally around 5000k
Warm White is on the extreme end, it is very yellow like the color of a incandescent bulb. It has the highest CRI so it is great for outside but inside it can get annoying when white wall hunting. It is generally around 3000k.
The tint is defined by a number followed by a letter, an example of this would be 3C. If the number is a 0, 1, or 2 then it is most likely cool white. If the number is a 3, or 4 then it is most likely a neutral white. If the number is from 5 to 8 then it is most likely a warm white. The reason I say most likely is because I am not specifying the letter.
Note: Going off the the Cree datasheets 5 is NW, but I find it to be much wamer than neutral.
To determine what the tint is like one can refer to this image.
To get an idea of what different kelvin ratings are like one can refer to this chart which shows them more clearly than the above one.
Brightness Bins
For XM-Ls the brightness bins range from S4 (which is the least efficient) to U3 which is the most efficient. The order is S4, S5, S6, T2, T3, T4, T5, T6, U2, then U3. Most lights are a T6 bin unless otherwise specified.
In between bins there is an approximate 12% difference in brightness but depending on the efficiency of the LEDs it can be as little as 0% and as much as 26%. These are both extreme examples based on the fact that a bin can vary as much as 7% and there is a 12% average difference between different bins.
Part of the reason that there is a variation in efficiency is due to the amount of phosphor on top of the LED die. The purpose of the phosphor is to convert the blue light produced by the LED to a more white or yellow light. Naturally as the amount of phosphor increases less light passes through it. This is why a warm white LED is going to be a lower bin than a cool white.
Below someone asked the question of why a blue LED does not produce as much light as a white LED even though theoretically there should be more light. After some research on the topic I found out that this is because the eye is very sensitive to white or yellow light, but very insensitive to blue light.
So sadly, we will most likely never be able to get a 1000 lumen 10 watt blue LED.
Recently, (December 2012) cree released the XM-L2, which is approximately 20% more efficient than the original XM-L. This means that a XM-L2 T6 is approximately as efficient as a XM-L U3. Unless it is specified, the light does not contain a XM-L2.
Interpreting The Specs of a LED
So now we know the basics of how a LED is rated now. So let's say you see XM-L T3 7B for sale. Now you know that will be less efficient, warm white, and an XM-L.
CRI stands for Color Rendering Index. The CRI of sunlight is 100, the CRI of our average CW LED is closer to 65. NW is approximately 75 and some WWs get to 80. Naturally you want as high of a CRI rating as possible so it is easier to distinguish between different colors.
A high CRI does not always mean it has a low kelvin rating, but it generally does. Nichia makes great Hi-CRI (high CRI) LEDs. Currently the most powerful one they make is the Nichia 219. It is slightly less powerful then a XP-G, is NW (5000k), and has a CRI rating of 92.
Links to XM-Ls-Based on Tint
Locating a XM-L with the tint you want can often be hard so I am going to paste links to a few different ones here.
XM-L 0D: 1,
XM-L U2 1A: 1, 2, 3, 4,
XM-L U2 1B: 1, 2, 3,
XM-L U2 1C: 1, 2,
XM-L U2 2B: 1,
XM-L2 T6 3C: 1,
XM-L 3C: 1, 2, 3,
XM-L 3B: 1, 2,
XM-L 5B: 1,
XM-L 5C: 1, 2,
XM-L 7C: 1,

I like the way this is going, thanks Scaru.

I haven’t seen many NW U2/U3 XM-L’s before… could you point out where I could get a XM-L U2 3C?

Merry Christmas. :santa:

So far there aren't any, (I'll change that example) but a XM-L2 T6 3C would be equivalent to a XM-L U3 3C.

Subscribed! Thank you for the chart scaru!

If they left off the phosphor completely, how high would the bin be, and what shade of blue?

It would be just like their blue XM-L series, at approximately 450-465nm.

The colored versions of XM-L’s are here: http://www.cree.com/led-components-and-modules/products/xlamp/arrays-directional/xlamp-xml-color

I don’t think they have color bins though.

I truthfully do not know, I can tell you when I have taken the phosphor off the LED in the past (while dedoming) it becomes a deep blue.

Based on that chart, I would say it was around 8000k. (general estimate)


As ryan pointed out, their blue XM-L is 450-465 nm so it would be a royal blue.

However, for what ever reason it seems that the blue LED in their colored XM-L is much less efficient than a white one. So now I am doubting myself. :( The white die produces 100 lumens at 350 mah and the blue one produces 13.9 lumens at 350 mah.


Off to go do some more research, now I am wondering whether the phosphor is needed to convert it to light in the visible spectrum.

nice run through scaru. Only niggle is that CW Cree LEDs are generally 65CRI, although the newer XM-L2 CW seem to be 70CRI. NW and warmer are 75CRI, one reason so many people like them over CW :slight_smile:

Added to the mod reference guide, this is brilliant, thanks scaru. 8)

Just changed it! Thanks. :)

This is what you’re looking for:
XM-L2 T6 5000k NW

Added a list of links to buy different XM-Ls based on tint.

Thanks for the link.

Mouser’s shipping is $20 for an $8 LED, so I think I’ll wait for FastTech to stock them. :slight_smile:

Thanks scaru for the effort. I understand simple.

Thanks scaru! I vote that this should be stickied…

Thank you scaru! Very well written. Nice reference and links!

Thank you

Thanks a lot for doing this Scaru, I like the way you put links to vendors of each of the tints available, I think this thread should be stickied

Thank you!

That’s what I don’t understand. If it is more blue and brighter the less phosphor, why are blue xml dimmer? I don’t think there is any way to “redome” an led after stripping the phosphor is there?

I doubt one could do it without losing even more light.