[argyllcms] Re: Question regarding Profile Validation
- From: "Brad Funkhouser" <brad.funkhouser@xxxxxxxxxxx>
- To: <argyllcms@xxxxxxxxxxxxx>
- Date: Wed, 05 Nov 2014 07:13:48 -0600
Robert,
I think those results are actually very good. The average error is
imperceptible to the human eye.
Read the last line of colprof's output from when you built the main printer
profile. It tells you what kind of errors to expect based on how it had to
structure the mapping given the patch data it used to build the profile.
There are compromises being made in the algorithm between exactness and
smoothness. That paper has a large gamut, probably a million different
perceptible colors, and you're building a mapping into it from a couple
thousand data points, each of which has it's own measurement error. And
since the original target spread you used was not perceptually uniform, some
of those data points are going to be pretty far apart, like dE 20 or 30 or
maybe 40. Then there's interpolation going on between those far apart data
points. It's a bunch of compromises, and when you take it all into
consideration, an avg dE of 0.717430 seems pretty darn good to me!
For the 100 patch test target, you could have it be perceptually uniform
within the printer space by adding " -I
-ciPF6400-Canson-Baryta-310-Argyll-2584.icc " to targen. That would be a
better test spread.
For the main target, you could use a preconditioning profile to get a
perceptually uniform spread which would even out your data points.
Thanks.
- Brad
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