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White level (data maximum) is

White level (data maximum) is not as easy as it should be.

LibRaw provides (estimated) data maximum in imgdata.color.maximum. This value is
- either hardcoded (this is derived from dcraw.c)
- or last item of linearization curve
- or determined using camera bit count

For many formats/vendors/settings it is correct, for others it is overestimated (for example, Panasonic low ISO w/ full-well limited sensor, also Canon's intermediate ISOs)

Also, there is imgdata.color.linear_max[]. If filled (nonzero) this value(s) represents vendor suggested white point parsed from metadata. This value is usually way too low (there are a lot of pixels above this threshold), but it is (yes) suggested by vendor.

Also, there are vendor-specific values in parsed metadata fields (e.g. canon.NormalWhiteLevel/canon.SpecularWhiteLevel)

-- Alex Tutubalin