[argyllcms] Re: Black point

  • From: Graeme Gill <graeme@xxxxxxxxxxxxx>
  • To: argyllcms@xxxxxxxxxxxxx
  • Date: Fri, 04 Feb 2011 12:29:00 +1100

Klaus Kompatscher wrote:
On my opinion this should not happen although magenta is replaced with
brown. All colors ti3 file with about max. ink amount (270%) show a much
lower L value.

In V1.2.0, I changed the black point code (at various peoples prompting)
to be the darkest neutral value. Prior to this, it was the darkest color
with the same hue as the black ink.

Because the change of ink skews the gamut, the black point is "correct" -
ie. it is the darkest neutral point. Note that this only affects the black
point tag in most profiles, but will have an effect on any gamut mapping
applied to the perceptual and saturation tables, if it is invoked.

This may not be what you want for this particular device, but the question is,
what black point do you want ? Picking the darkest possible point (for 
would result in poor neutrals for many devices.

The thing is that the gamut mapping isn't set up for your particular
problem. The device behaviour you have is almost 2 dimensional,
and a gamut mapping that can properly map from 3 dimensions to 2
is what you need.

Graeme Gill.

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