I am using libraw to access cam_xyz and cam_mul to compute the Color correlated temp and tint of an image.
When the RAW comes from a non supported camera, cam_xyz is a matrix filled with zeros.
Is there a recommended way to fallback on cam_xyz values coming from a different but similar cameras (same brand, earlier models) and compute an approximate value rather than returning some default temp and tint.
I do not think that fallback
I do not think that fallback to older model is safe. Newer camera may have different sensor, or different CFA filters, or different calibration, or different raw adjustments in firmware. You could not know it without new raws analysis.
-- Alex Tutubalin @LibRaw LLC