[argyllcms] Re: Scanner profile

  • From: Graeme Gill <graeme@xxxxxxxxxxxxx>
  • To: argyllcms@xxxxxxxxxxxxx
  • Date: Wed, 08 Sep 2010 23:17:14 +1000

Klaus Kompatscher wrote:
I get a scanner profile (colprof) with too high DE >40.

Hmm. I'm not quite able to reproduce that. Using the default cLUT
type profile, I get a worst case error of 16, average 3.5, which
isn't fabulous, but doesn't seem inconceivable either.

The procedure:
- I create my own target with ./targen -v -d 3 -s 21 -g 21 -f 513  -c
Cruse_LRFB.icc Scanner   (ti1 file attached) by using a previous icc profile
of the same scanner.

Why are you using the scanner profile to create the print chart ?
You want the print chart to have well spread colors in the available
printer gamut, so you should use the printer profile for this.

Ideally you should opt for full perceptual distribution and no curvature
distribution (because you aren't interested in mapping the printers
behaviour), so I'd recommend using the (undocumented) options "-A p1.0 -A c0.0"
instead of the default or the combined -A adaptation value.

I double checked all data and it looks good to me, nevertheless the profile
is unusable.

It's hard to tell what could cause such problems. I would suspect the reference
values, but there is nothing as obvious as completely scrambled sample values, 
the less the sorts of errors I get for a gamma/matrix profile and the 
of the fit errors suggests something is not right with either the reference 
or the scanner .tif file (channel values being clipped ?)

Graeme Gill.

Other related posts: