Hi List,
Been hitting a wall with what seems like a simple problem.
My starting point is the spectral color corresponding to 430 nanometers, some
violet. The problem is that I don't understand how to obtain RGB values from
the CIE 15.2 1931 chromaticities.
Is there anything, in Argyll color utilities, that I could use to figure out
what RGB values to use for spectral colors?
430nm CIE x,y = 0.1635, 0.0069
I don't have a "real" value for Y, not even a Luminance factor that I could use?
All I know is that, to "qualify" as a "credible" shade of Violet, with good
saturation, it can't be too light of a shade. It could not be like with an CIE
L* = 60 or higher? It has to be below 40, possibly 30 or 26.
With some algebra, I convert the above CIE x,y value to CIE XYZ tristimulus
values, some suspicious large numbers, like X = 1600 Z = 600. And then I
convert to RGB through an adapted matrix of some kind.
I get some RGB values like, Blue is always at 255 and Red varies between 32 and
78. Green is always zero.
Now, those various Red numbers, I get because I change the Y value in the XYZ
to RGB conversion.
I tried using as low as a value of 1 to 100, by step of 10.
But I am wondering whether I use the right method?
What is difficult is that, to the best of my understanding, the 1931
chromaticities are all relative to the Equi-energy spectrum? Meaning that they
are all expressed on a Unit Luminance scale? That's the limit of my
understanding.
I know I have to continue my research but any help is appreciated.
Ultimately, what I'd like to be able to do is to calculate RGB values for all
the spectral colors for the 1931 Observer for D50/D65 illuminant...
Best / Roger Breton
www.graxx.ca