[argyllcms] Re: RGB Printer Profiling / Issues with Blacks and Shadows
- From: Graeme Gill <graeme@xxxxxxxxxxxxx>
- To: argyllcms@xxxxxxxxxxxxx
- Date: Sat, 06 Aug 2011 11:49:51 +1000
Andreas Hebeisen wrote:
> Meanwhile I've found a reliable method to simulate the problem, without the
> need to print. If
> you like, I can send you two PDFs which show the evaluation image I'm using
> but with the color
> corrections applied from Aperture using either the eyeOne-iMatch or the
> ArgyllCMS-profile. But
> they're pretty big (around 45Mb each), so I'll just send them if you really
> want.
Sorry, I doubt that would help. The important bit is what's going on in the CMM.
> Hmm... Can't really follow, but sounds bad.
There is a degree of ambiguity in V2 specifications regarding white point, and
the ICC meddled with the black point treatment in the PCS, leading to even more
variations in profile behaviour.
Changes in the nature of the measurement mode (contact vs. telescopic) in V4
have thrown in additional complications to muddy the waters.
> Since it seems to bee a big secret which color space Aperture uses internally
> before sending the
> files to the printer driver, one can only guess which input profile would be
> best.
The perceptual and saturation tables are not going to be very predictable if you
don't know what colorspace is being fed into them. That profile needs to be the
one
specified in colprof. If the internal space has a black point with a high L*
value, and the perceptual and saturation table are expecting a low L* black
point, you will get the effect you have seen. I have no idea though why
the profile maker profile should be any different though.
Graeme Gill.
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