Hello,
I've had this thought in my mind for a while. I'm referring to adjusting color (such as saturation and color contrast), in particular with the ab-curves in the tone curve module. When I change these, they will in general act nonlinearly on the a- and b-channels.
Now what I'm wondering is this: The a- and b-axes are somewhat arbitrary within the chrominance place (I'm sure they have been chosen for a reason, though). In other words, I could have different axes u and v obtained by rotating a and b around the origin (i.e. gray) by some angle phi (this should be equivalent to converting to LCh and shifting h by phi), and have my nonlinear adjustment curves act on u and v values. Note that due to the nonlinearity I cannot achieve the same transformation on a and b directly with appropriately different curves. Even with just a linear scaling (color contrast module?), it is not as general since arbitrary nonuniform scalings in 2d-space require a third parameter as they are described by symmetric 2x2-matrices.
Thus I'm effectively proposing a family of colorspaces Luv parameterized by phi, of which Lab is a special case (phi=0).
The reason why this came to my mind is that with the a/b-curves it's not always easy to get the colors the way I want them. If for example I emphasize green (by boosting negative a's), I just don't get the right tone for foliage.
Now I'm wondering if this consideration makes sense at all. Maybe it won't help at all. Just wondering what y'all think.
Stefan
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