I know that my Canon camera's raw offset is meant to be 2048, however often libraw reports slightly different values in rawdata.color.black like 2044 for instance. Which one is more accurate? The reported value seems like it might be prone to being influenced by noise. Can the true offset vary this way or should I take libraw's reported value as an approximation of the ideal value? And if libraw's value is to be trusted then why is that?
Using 2044 instead of 2048 can result in blacks being raised to a value of 1 (in 8-bit sRGB) and proportionally more if the gain is boosted as well as with WB corrections (for instance on a night shot it can easily raise blacks on the blue channel to 7 in sRGB), so this is quite important.