Hi folks,
I had a conceptual question about white balancing and its impact on matrices such as rgb_cam and cam_xyz.

My understanding of white balancing is scaling the relative amounts of R, G and B depending upon the source illumination. There is a paper (cited by many sources) by Viggiano (http://acolyte-color.com/papers/EI_2004.pdf) that states that best results are obtained when white balancing is done on the CFA data. Hence, we scale the CFA data using the multipliers.

My question is the following:

WBCT_Coeffs give white balance multipliers for different camera presets. This is true for CR2 files that I have examined. Each white balance multiplier corresponds to a specific illuminant (Daylight vs Cool vs Tungsten) as defined by the LightSource EXIF Tag. These are different from D65. So, how can we use the rgb_cam matrix or the cam_xyz matrix for color conversions without doing a white point adaptation because both these matrices assume a D65 white point?

Conceptually, I do not understand how scaling the CFA data using the white balance multipliers makes "white" appear as it would under the specific illumination but we can continue to use matrices that are derived against D65?

Maybe this is something trivial, but I am quite new to white balancing and so am not very clear about this.

Regards,
Dinesh