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Steve Kale wrote:
I understand that the CIELUV space is still preferred by many working with
video. In fact I've heard one commentator say that CIELAB is preferred for
reflective media applications but CIELUV is preferred by those working with
emissive applications. I find such comments puzzling as I had always
thought that CIELAB had proven itself over time to be the more "robust" (by
which I assume people mean "more perceptually uniform") colour space and
that computation of colour differences using LAB-based dE equations (1994 or
2000) represented best possible estimates of perceived differences in
colour. Else one would have thought that LAB would have died by now.
(Furthermore, I don't understand why one perception of colour would depend
on emmission/reflection.)
So is there any basis for using LUV or is this just a case of old habits die
hard?
Originally, the judgement was that CIELAB and LUV were different,
but roughly equivalent in how well they represent a uniform
perceptual colorspace - ie. much better than XYZ, Yxy, but far
from perfect. LUV has the advantage that it is a more linear
transformation in the hue plane from XYZ than CIELAB, and
therefore favoured for things like (more) perceptual chromaticity
diagrams, and chromaticity diagrams are things display people
love, because they are working with essentially linearly additive
devices.
It's also fair to say that all the activity in improved color
difference metrics such as CIEDE94 and CIEDE2000 are based
on CIELAB.
It does seem that the development of CIEDE94 and CIEDE2000 have
predominantly used surface matching data sets, and
therefore may well have ended up with a metric that is more
suited to reflective color viewing situations, but the CIEDE2000
paper does show results of various CIELAB based color
difference formula on a CRT matching set, and CIEDE2000
seems to fair very well, although there is no direct comparison
to LUV DE.
> Ok so I'm way behind the curve! I've just not seen CIECAM02 deployed in any
> of the tools I use, eg Photoshop.
Be careful. CIECAM02 is a color appearance space. Human perception of
color is weird enough that it does not automatically follow that
a good color appearance space makes for a good color difference
space, although there are some papers that investigate using
CIECAM02 for this purpose.
