Converting Temperature to Color

Spencer W. Thomas (, 01 Feb 1995

If no one else responds, here's how to do it from first principles:

  1. Find the equation for the black body spectrum.

  2. Convert the spectrum to RGB. See, e.g., Hall: _Illumination and Color in Computer Generated Imagery_, Springer Verlag, 1988. I bet there's code in an online archive to do this, too.

Spencer W. Thomas (, 02 Feb 1995

Find the equation for the black body spectrum.

Ok. Here it is, from the CRC Handbook of Chemistry and Physics, definition of Radiation formula, Planck's:

The emissive power of a black body at wave length lambda may be written

    E(lambda) = c1 * lambda^(-5) / (exp(c2/(lambda*T)) - 1)

where c1 and c2 are constants, with c1 being 3.7402e10 microwatts-microns^4-per-cm^2 or 3.7403e-12 watt-cm^2, c2 being 14384 micron-degrees and T the absolute temperature.

If you're just looking for the shape of the spectrum and not the absolute brightness, you can, of course, ignore c1.