Re: Real world experience w/ GMG and Oris RIPs
Re: Real world experience w/ GMG and Oris RIPs
- Subject: Re: Real world experience w/ GMG and Oris RIPs
- From: Graeme Gill <email@hidden>
- Date: Fri, 26 Nov 2004 09:10:04 +1100
- Organization: Color Technology Solutions Pty. Ltd.
Roberto Michelena wrote:
in the iteration. And also in the fact that usage of link profiles, by
interpolating in the same space of the end result (CMYK in this case), can
increase the fitness of the interpolation algorithm compared to
interpolating in an intermediary space (Lab or XYZ) which has different
properties.
I think that this is the key real world advantage of an iterative approach
applied to a proofing workflow (CMYK -> CMYK). The idea would be to reduce the
compound errors of the source and destination profiles (i.e. approximately
halving the overall errors compared to other conventional systems, everything
else being equal.) It also has the effect though, of reducing the errors for
the particular test values being used in the iterative tuning, to values
close to zero. If these same values are used for verification, then an
artificially good impression could be made as to how much real improvement
is gained.
Other approaches (such as the one I generally use, which is to create
a device link profile by linking the source profile with an inverted
forward table of the destination profile) probably have errors that
are better than conventional systems, but may not be quite as good as
an iterative approach.
Tightening -by iteration- the match of your profile's output gridpoints,
however, should provide nothing but benefits. I don't know why they don't do
it!
I'm not sure I follow you there. I certainly can't see any point of using
iteration purely on an output profile. The forward profile has been
determined by the sample points, and can be arbitrarily accurate when measured
against those sample points, and the output profile is just the inverse of
the forward profile, which once again, can be arbitrarily accurate
when measured against the forward profile. Any meaningful iteration could
be done purely in software. Of course the number and location of the sample points,
together with the profile model and model fitting algorithms, will have a great
influence on the real world output profile accuracy.
Graeme Gill.
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