[argyllcms] Re: Scanner profile

  • From: Klaus Kompatscher <kkompatscher@xxxxxxxx>
  • To: <argyllcms@xxxxxxxxxxxxx>
  • Date: Fri, 05 Nov 2010 19:11:14 +0100

Hi Graeme

finally I found some time to follow up your indications and to do some more
tests, but:

On 08.09.2010 15:17 Uhr, "Graeme Gill" <graeme@xxxxxxxxxxxxx> wrote:

> 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.
It seems targen does not accept a cmyK pre conditioning profile (printer) to
create a RGB test chart -- Error - ICC profile doesn't match device!
How can I use the printer profile?

> 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,
> none
> the less the sorts of errors I get for a gamma/matrix profile and the
> distribution
> of the fit errors suggests something is not right with either the reference
> values,
> or the scanner .tif file (channel values being clipped ?)
> Graeme Gill.

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