I was hoping some of the regular more experienced guys might chime in with some explanation and discussion about dE. How it is measured/expressed is a little fuzzy to me. ?
Originally Posted by krasmuzik
I do not agree with using CIELAB for displays - as it was more intended for the paint and textile industry where the apparent surface color varies depending on the color temperature of the illumination. CIELUV was intended for the light source itself. This is why CIE 1976 could not settle their differences - and they picked both color specification. And most of the improved color formulaes have worked on the surface color issues.
An excellent resource for those that want to play with color formulas is
Originally Posted by Ursa
Jeff has it. Poynton just uses the 1976 version, and as Bruce Lindbloom points out, it is flawed.
The 1976 method is heavily dominated by the L* component of either the CIELab or CIELuv coordinate systems. Thus, grayscale error is represented in both the dL* component, and in the du* and dv* (or da*, db*) calculations. "Delta C" (dC*) eliminates the L* component, but does not eliminate the impact of luminance entirely from the calculation (L* is used as a scaler when converting xy -> u'v' -> u*v*).
Originally Posted by gregr
When we use dE* as a metric for grayscale tracking we wish to describe the color difference between an actual grayscale color and the D65 reference color, both at the same lightness. Therefore L* = 100 and delta L*=0. Hence, L* becomes a fixed scale factor in the dE* calculation. If we want to express luma errors in the grayscale tracking we show that separately as a gamma error.