[Radiance-general] More on Color Temperature

[Nick Calcagni]

In regard to the below message, how does one determine RGB values from a
point of choice in Radiance? I cannot use Radiance yet, but I am just
interested in the code, if it is possible. I would just like to use Radiance
to compare how different luminaires render color differently, and how
varying surfaces appear differently under those lighting conditions. So you
can see I am not interested in the RGB values of the light leaving the
source, but rather the RGB values of the surface which we see.

Thanks,
Nick Calcagni

I hope that makes sense...

Hi

It may be possible to estimate the color temperature from the RGB
Radiance channels by:
1) transforming the RGB values into xyz trilinear coordinates

2) using an approximate formula relating xyz to color temperature.
See for instance this paper:
McCamy, Calvin S. (April 1992). "Correlated color temperature as an
explicit function of chromaticity coordinates". Color Research &
Application 17 (2): 142-144

http://dx.doi.org/10.1002/col.5080170211

Hope this will help you.

Raphael Compagnon
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