[argyllcms] Re: Characterizing a scanner using Argyll

  • From: Graeme Gill <graeme@xxxxxxxxxxxxx>
  • To: argyllcms@xxxxxxxxxxxxx
  • Date: Mon, 02 Feb 2009 11:52:15 +1100

Asman, Andrew J wrote:
compared to the Gretag Spectrolino is consistently under 2. However, if I 
measure pages
using a printer that has a larger gamut than the one used to create the 
profile, then
the out-of-gamut colors tend to produce extremely large max delta E value 
anywhere up to 100 depending on the printers used.

It's no surprise that extrapolation is much less accurate than interpolation,
and that the further away from measured values you get, the worse the error.

Is there any way to increase the accuracy of the profile when faced with 

I'm surprised to hear of delta E's as large as 100, unless you are 
significantly out
of gamut. The best way of addressing this issue is simply to expand the gamut
of your test chart to include these colors. The other approach is to try and
choose a model that better represents the underlying characteristic of
the device, rather than being as general as clut. You could try shaper/matrix,
or gamma/matrix for instance, but you will probably be trading off a worse
in gamut fit for a better out of gamut fit. This is assuming that the scanner
has an underlying behaviour that is close to a per channel compression curve...

Graeme Gill.

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