Klaus Karcher wrote: > I inspected the XYZ CLUT profile and noticed that the A2B tag contains > the identity matrix. > Could XYZ CLUT profiles with "real" matrices be an option to improve > scanner profiles? The model of a "lut16Type" for the A2B tables is RGB -> matrix -> shaper -> CLUT -> shaper -> PCS. So I'm not sure, whether using this matrix makes sense for non-linear RGB. If we assume linear (gamma 1.0) RGB (e.g. raw data from the sensors), and if we populate this matrix with an approximate RGB -> XYZ transformation, then it would likely shrink the coverage of the CLUT, resulting in the need for a CLUT with an even higher grid resolution in order to achieve the same accuracy. More appropriate would be IMO rather a matrix, which maximizes the CLUT utilization for the set of all valid RGB triples which can be returned by the scanner, while still producing non-negative numbers after applying the matrix for all valid RGB triples which can be returned by the scanner. BTW: The ICC spec also sais that the matrix shall be the identity matrix unless the input color space is XYZ. So w/o violating the ICC spec, using the matrix seems not to be an option at all, though I guess that most CMMs won't care and will honor a non-identity matrix also for input color spaces different from XYZ. Regard Gerhard