Roberto Michelena wrote:
It seems to me that CIE X,Y,Z are the best choices; extend better than densities (do not level off so quickly), are much less noisy... X for Cyan, Y for Magenta, Z for Yellow, and any of them for Black.
Another way is the dot product with the vector to the 100% colorant value to white (or some other choice related to the underlying colorant vector direction) in a particular colorspace (XYZ, L*a*b* etc.). This could be viewed as creating an "optimal" mix of the co-ordinates as a measure, rather than just picking one of the co-ordinates. XYZ isn't a good choice as absolute measure, as it is linear light, so the blacks steps will be too big. A gamma or L* curve applied to XYZ is needed at least. Density is a log scale, which is why it's not too bad, although in the Colorbus calibration system I set a target density curve corresponding to a typical 20% dot gain press curve. Graeme Gill.
