[argyllcms] Re: targen and profile
- From: "Roberto Michelena" <colorsync@xxxxxxxxx>
- To: argyllcms@xxxxxxxxxxxxx
- Date: Thu, 22 Feb 2007 18:36:37 -0500
my experience is that the verification result depends significantly on the
distribution of the test set points used to assess the "resulting profile
accuracy". My feeling is that I get in a majority of cases better average
errors, whenever the same kind of distribution is used for both, the training
set and the test set.
This sounds quite obvious, or am I reading it wrong?
Basically you're saying "if I profile or refine with an ECI2002, and
then I use an ECI2002 to verify, I get better verification results
than if I use another patch set to verify".
This is why I don't like those shootouts (IPA, Wuppertal, WMU) in
which they always do that. You'll never know if an iterative-kind
software (proofing or profiling) optimized the test chart patches in
detriment of the profile's accuracy in other colors, or general
smoothness.
I remember someone posting a comparison (before and after) picture of
PrintOpen 5.x CMYK separation of an RGB 'rainbow hexagon', in which
after refining the CMYK profile by iteration (PrintOpen 5.x has this
feature), it looked awfully un-smooth.
My take: you should evaluate BOTH the same testchart which is used to
refine, and another one composed of semi-random in-between points. And
they should be evaluated separately, so that you can see whether the
error decreases on both, or at least does not increases in any.
-- Roberto Michelena
Infinitek
Lima, Peru
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