Re: MeasureTool Compare question
Re: MeasureTool Compare question
- Subject: Re: MeasureTool Compare question
- From: bruce fraser <email@hidden>
- Date: Mon, 14 Mar 2005 09:26:31 -0800
At 9:01 AM -0600 3/14/05, Matt Nelson wrote:
I must really not be awake this morning, I'm apparently doing this
wrong. Is not one of things first things one should do after
outputting a test chart, measuring it, building a profile for the
device, and then outputting a corrected chart using the profile
created,
is to first compare the uncalibrated output to a known reference,
and then to compare the corrected output to the known reference to
see if the profile worked? I can open the measured chart data in
Compare, but which file are you supposed to use as the reference? I
did this before in ProfileMaker 4's measure tool, but everytime I
try to open the reference text file for the chart, I'm told it
"doesn't contain measurement data of CIE type (error 20718)" so I'm
obviously doing it wrong.
The target reference files just contain the CMYK or RGB values for
the patches. You need to compare measurement files.
What I do.
I make the profile from measurement file 1.
I assign the profile to the testchart, convert it to Lab, save the
Lab values as measurement file 2, print it, measure it, and save
these measurements as measurement file 3.
I now have three sets of measurement files.
Measurement file 1 is the actual device behavior.
Measurement file 2 is the device behavior predicted by the profile.
Comparing it with measurement file 1 lets me see the error in the
AtoB tables.
Measurement file 3 is the behavior produced by the profile. Comparing
it with measurement file 2 shows the error in the BtoA tables, which
is almost invariably higher.
Finally, comparing measurement file 3 with measurement file 1 shows
you the overall accuracy of the profile.
This exercise is mainly useful for evaluating profile edits-usually
they improve something at the expense of something else-or for those
of us who want to put a metric on everything!
--
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