[argyllcms] Re: optimizing target generation, linearization, etc.

  • From: Gerhard Fuernkranz <nospam456@xxxxxx>
  • To: argyllcms@xxxxxxxxxxxxx
  • Date: Sun, 28 May 2006 00:24:53 +0200

Roberto Michelena wrote:

Then I pass the "P2P19" target (the one used by the Gracol7 folks) through the profile, in order to get Lab values; it has grays and primary and secondary ramps. When plotting these points it seems obvious why the green area plotted so badly. The "hooks" formed by the green ramp are terrible,

I think what I can see is not so unusual for inkjet printers, i.e. that the a* or b* vs. colorant curve sharply bends shortly before reaching 100%. Some folks recommend not to drive the printer to its extremes, but to utilize only approx. the lower 90% (or wherever the sharp bending starts) of each colorant. I'm not sure what I should think of it, as I guess that this strategy also sacrifices some amount of the printer's gamut, but of course it avoids the nasty problem of extreme curvature shortly before saturation, giving an overall smoother response. Another possibility to reduce curvature might be a linearization which stretches the current range 90..100% to say 70..100%. However, I'm not sure either, whether it is a good idea to waste precision in large parts of the gamut, just to get a small subset of the gamut characterized more accurately.

Regards,
Gerhard



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