From Mark's essay:
CR Curves have a hue lock. They map the minimum and maximum RGB values (in linear ProPhoto RGB) through the tone curve, and the middle value is interpolated to exactly preserve hue. The PS-RGBc does not have a hue lock. But setting the PS-RGBc to Luminosity Blend Mode preserves the colour of the underlying layer. Using the Lab L*Curve for this purpose has only fair colour consistency as L* is changed holding a* andb* constant.
1. Does the CR curve, then, exactly preserve hue even with the mild saturation changes?
2. If so, must one continue to work in ProPhotoRGB when in PS to realize this advantage? Can Adobe RGB also preserve exact hue?
3. I think I understand that (in LAB) a* and b* do not remain constant as to hue as the L* is changed; they drift slightly. But in the PS-RGB curve is the hue exactly preserved in the Luminosity Blend Mode? Would this be this considered "locking" the hue, at this point?
And another question : It seems that a great deal of the successful manipulating of the ACR/LR curve is due to the effective placement of the exposure zone spacers. How does one best approach that task?
And thanks for the great article!
