Re: Is a printer's full gamut used to make a profile?
Re: Is a printer's full gamut used to make a profile?
- Subject: Re: Is a printer's full gamut used to make a profile?
- From: Steve Upton <email@hidden>
- Date: Tue, 18 Sep 2001 15:16:45 -0700
At 7:55 PM -0700 9/14/01, Randy Wright wrote:
I have been comparing profiles made with ColorVision
Profiler Pro for RGB photographic printers with the
spectro measurements used to create the profile, in
ColorThink. ColorVision uses a target made up of
uniformly-incremented samples of all the possible
color combinations. If you view the patch readings in
ColorThink's 3D Grapher, they appear as concentric
layers. When the profile is superimposed on the
measurements, its outer limits lie for the most part
between the outermost layer of readings and the next
one in. In some areas, it goes in past the second
layer to the third. This seemingly indicates that the
full gamut of the printer is not being used. Is this a
common condition? Is it even significant? I don't have
any other profiling packages with which I could make a
comparison.
Ok - bear with me here....
The first test you want to do is to see if the proofing side of the
profile is doing a good job. (CMYK->Lab)
So try this:
- open the original CMYK reference file into ColorThink as a Color
List - this may not be available with Profiler Pro. If not, I think
you might need to make it by hand. Copy one of the CMYK stunt files
and replace it's numbers with the ones that you sent to the CMYK
printer using Profiler Pro. They need to be in the same order as the
ones in the measurement file.
- drag your profile onto the Color List - this will "proof" the CMYK
settings into Lab using the profile. This is the profile saying "I
think this is what these CMYK values will look like if sent to that
device".
- open the measurement file (Lab data) into ColorThink. -Now you have
the ACTUAL readings in comparison to the previous step's profile
"speculation"
- drop each list into the 3D grapher and select "Vector Compare". Then graph.
ColorThink will graph the differences between the measured colors and
the predicted colors. If the color shift vectors aren't too big, then
you can have some confidence in the proofing side of the profile. If
they are large and all over the place then the proofing side of the
profile is bad. ColorVision's profiles have not really been known for
their proofing accuracy, Profiler Pro should do a better job as it
has instrumented measurement data to go by.
These steps and tests are undergoing a fairly major revision in
ColorThink 2.0 to make them easier and faster to do. Once you find
that you are happy with the proofing side of a profile you can do
some round-trip tests with profiles that can illustrate rendering
intent behavior quite well... ya'll hafta stay tuned fer that...
Or better yet - Go To Seybold!
Regards,
Steve
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Steve Upton
CHROMiX / Profile Central
www.chromix.com www.profilecentral.com
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