Relative Luminous Values in RGB Mixing

hamilton · May 19, 2010

Hi all,

I am working on a fairly high powered RBG mixing project, but I've hit a bit of a mental snag.

What are the relative intensities I need between my RGBs to make white? I seem to remember something like 60 percent green, 30 percent red and 10 percent blue, but I'm not totally sure on that.

So, for example, if I had a 60 lumen green LED, a 30 lumen red, and a 10 lumen blue, the result would be white.

Does anybody know what the (roughly) correct combination for this is?

Thanks,

James

copperfox · May 19, 2010

I don't know, but this thread is interesting. :popcorn:

gswitter · May 20, 2010

hamilton said:
What are the relative intensities I need between my RGBs to make white? I seem to remember something like 60 percent green, 30 percent red and 10 percent blue, but I'm not totally sure on that.

That's the simple luminance ratio I've used for converting RGB images to monochromatic.

How are you measuring the individual color outputs?

jtr1962 · May 20, 2010

This might help. Of course, slightly different center wavelengths will alter the ratios somewhat, but you should have a good starting point.

Özil · May 21, 2010

Do I see this correct: If I have an RGB LED and I misc it like the last solution:

9300 29.5%R, 36.3%G, 34.2%B

I will get a colour temperatur of nearly 10.000K?

jtr1962 · May 22, 2010

Özil said:
Do I see this correct: If I have an RGB LED and I misc it like the last solution:

9300 29.5%R, 36.3%G, 34.2%B

I will get a colour temperatur of nearly 10.000K?

No, those are the ratios for the table using particular red, green, and blue LEDs which the author chose to use.

The table for the actual percentages of red, green, and blue lumens is found right on the bottom of the page ( I copied it below ). For 9300K it would be 25.9% R, 61.4% G, 12.7% B. The table assumes 625 nm red, 525 nm green, and 470 nm blue, all of which are easily available. Amazing how little blue is needed even for higher color temperatures. Also note that for all the color temperatures except 1900K the percentage of green lumens is 60%, give or take a few percent. Basically then, color temperature is mostly changed by varying the proportion of red and green lumens making up the other ~40% of the output.

Code:

Color temp. K    % from red  % from green  % from blue

1900             50.69%      48.99%         .32%
2700             40.5%       57.5%         2.0%
3000             38.15%      59.12%        2.73%
3500             35.2%       60.9%         3.9%
4100             32.7%       62.0%         5.3%
4500             31.5%       62.35%        6.15%
5000             30.25%      62.6%         7.15%
5500             29.3%       62.65%        8.05%
6500             27.9%       62.5%         9.6%
9300             25.9%       61.4%        12.7%

x=.333 y=.333    30.2%       61.3%         8.5%