Re: MeasureTool Compare question
Re: MeasureTool Compare question
- Subject: Re: MeasureTool Compare question
- From: Chris Murphy <email@hidden>
- Date: Mon, 14 Mar 2005 09:11:19 -0700
On Mar 14, 2005, at 8:01 AM, 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?
No. A profile doesn't correct output. The profile is merely a snapshot
of actual behavior of the device for which it was made. The theoretical
test I do is converting a Granger Rainbow or Don Hutcheson's
RGBXPLORER8. You can assign your preferred RGB editing space to these
targets, then convert using your new output profile you're testing as
the destination. Any unusual behavior, like massive posterization, is
often indicative of bad measurement data. Moderate posterization could
be either bad measurement data or a less than stellar behaving output
device.
The practical test I do is with a series of tagged images, both RGB and
CMYK, representing a wide range of colors and tonality, convert them
with the new profile, and inspect the conversions. It can also be
useful to output the converted files on the actual output device.
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.
Measuretool's Compare function compares device independent values
between two data sets. The reference text file doesn't contain LAB or
spectral values which is why you are getting the error message.
Chris Murphy
Color Remedies (TM)
www.colorremedies.com/realworldcolor
-------------------------------------------------------------
Co-author "Real World Color Management, 2nd Edition"
Published by PeachPit Press (ISBN 0-321-26722-2)
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