For no other reason than to improve my understanding of what happens in a raw processor, I have been trying to do my own calculations of converting white balance multipliers to color temperature. There are two steps involved
Convert WB multipliers to a color in XYZ space by multiplying the inverses of the multipliers by a camera profile matrix for my D610
Convert this color to a color temperature
I have the second step under control but have some doubts about the first step. The only way I can get sensible results is to modify the multipliers so they represent the wb correction for the illuminant only, ie by removing the contribution from the uneven spectral response of the sensor. To do this however requires me to estimate the wb multipliers for the sensor alone (ie for an illuminant with uniform spectrum). I am doing this by integrating the spectral response curves of the camera channels across the wavelength range. I have a reasonably reliable set of data for the D700 which I suspect is similar to the D610 in terms of channel spectral response.
This seems to work OK however I wonder if there is an easier way? I wonder for example what you do in Fast Raw Viewer?
Thanks and regards