[argyllcms] Re: Absolute colorimetric - dark saturated colours excessively light

Gerhard Fuernkranz wrote:

Some folks currently think that things are overly light, and under saturated (e.g. blues and greens).

actually this is my subjective impression as well - strongly saturated out-of-gamut colors are IMO rendered by Argyll's gamut clipping subjectively too ligh and not saturated enough, particularly in comparison to profiles from other profilers which seem to render them darker (resulting in a higher apparent saturation). 

It's very subjective, and it depends on the profiles. My "standard
test setup" is sRGB to CMYK Cromalin Proof, and of course the
RGB primary & secondary cusps are light, and the CMYK primary &
secondary cusps are dark (the cusps being the verticies with the
most saturated colors in a colorspace.)

It's also hard to keep perspective. When I look at the rather light
mapping V0.53 does I tend to think "it's not very saturated". When
I look at the more saturated mapping in what I'm currently working
on I tend to think "it doesn't have the same subjective lightness,
it looks too dark. I know I can make it lighter".

This implies, that Saturation can be increased by increasing Chroma (at constant Lightness), but also by decreasing Lightness (at constant Chroma). So I could imagine that the CUSP point of a gamut hull (in JCh space) for a given Hue angle (i.e. the point with the largest reproducable Chroma at the given hue angle) is not necessarily the most _saturated_ color which can be reproduced at this hue angle (but I have never verified this for real printer gamuts). 

I haven't noticed it working this way. The colors aren't really usefully
examined in isolation, so I'm not sure that the (appearance terminology
concept) saturation is relevant (since it is colorfulness/its own brightness).
[Above I am using the word "Saturation" loosely, I really mean "Chroma" in a
strict sense.]

Graeme Gill.



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