[argyllcms] Re: "RGB"-printer and inversion in blacks
- From: Nikolay Pokhilchenko <nikolay_po@xxxxxxx>
- To: argyllcms@xxxxxxxxxxxxx
- Date: Wed, 02 May 2012 12:12:30 +0400
I think it can be mode with clipping (the colorimetric intent nature), but not
just to minimum dE. The clipping may have grey monotonicity priority. I.e. If
the reverse colorimetric conversion leads to inversion of the lightness, the
new back point should be chosen (or another workaround performed) to achieve
the monotonic colorimetric grey gradient. As soon as the clipping exists, we
unable to maintain colorimetric precision. If so, why not to improve the
dark-gray behaviour by cost of slightly more dE?
Sometimes I recommend the users to try relative colorimetric intent because
it's most reality colors. In most cases the loosing of shadow details is OK,
but the inversion isn't acceptable. So I had to ask this profiler feature.
Graeme Gill wrote:
> Hi,
> from the look of the gamut hull, I think the device behaviour is
> fairly normal, and it is just a matter of dealing with the consequences of
> a device black that is not quite neutral.
>
> > May be there is an automatic work-around method possible
> > for such devices? I can imagine that the profiler performs the test like
> > mine automatically -
> > inverse then forward conversion of a grey gradient and the checking the
> > resulting gradient for
> > monotonicity. If non-monotonicity is detected, some work-around can be
> > performed while profile
> > re-computing. I think the gray scale monotonicity is the most important and
> > it's will be
> > acceptable to check only greyscale inversion.
>
> The intent (colorimetric) is not aiming for monotonicity, it is aiming to
> reproduce the color with the minimum delta E. The other intents (perceptual
> and saturation) are aimed at smooth and pleasing image reproduction (ie.
> monotonicity), while colorimetric would be used for things like spot colors.
>
> I am wondering though, whether there is a general expectation for an
> alternate colorimetric intent with clipping behaviour that does not return a
> minimum delta E, but instead have some other constraints. What constraints
> would that be though ?
>
> Graeme Gill.
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