Re: Target Reference file
Re: Target Reference file
- Subject: Re: Target Reference file
- From: david wollmann <email@hidden>
- Date: Fri, 16 Jul 2010 12:42:37 -0600
Date: Thu, 15 Jul 2010 14:07:59 -0400
From: Terence Wyse <email@hidden>
Now if you were to compare your printer profile to a "reference"
profile such as AdobeRGB, sRGB, whatever, you'd have something to
compare to.
In ColorThink I could look at both profiles in 3D and see how they
match up.
Is there something else?
Would the Gamut Volume be something to base an "optimized" printer
condition on?
A qualified "yes".....as long as you understand that gamut volume
doesn't necessarily mean you have a larger or more "saturated" color
gamut. Gamut volume is also affected by tone distribution or
"linearization". IOW, a better tonal distribution can result in more
achievable colors without actually "expanding" the boundaries of the
3D gamut plot. So gamut volume is both the outer boundaries or
"chroma" as well as the tonal distribution within the boundary.
Okay, that all makes sense and it expands and fills in my
understanding of Gamut Volume.
So lets say I have profile #1, then I decided to change the Ink
threshold for Cyan. I relinearize, print new targets and build
profile #2. In MeasureTool or ColorLab I compare the measurements
of #1 to #2 and it gives me Delta E values. How do I know if
profile #2 is better or worse? Sure there will be a difference but
what would I look for in the numbers to show improvement?
I'm not really sure if Delta E values would tell you much in this
context. It would tell you they were "different" but not which one
is better. I would look at....1) gamut volume 2) gamut "boundary" 3)
tonal distribution of the primaries/secondaries (change view to
"points" in CTPro and 4) the "Curves" display and neutral analysis.
The lower the chroma values along the neutral axis (using absolute
colorimetric), the better neutral stability the profile should have.
Okay, I like these check points. #3 is very nice, I had not used that
very much. When looking at the neutral analysis and the chroma values,
#4, the target in bottom right corner of the Profile Inspector-Curves
window in ColorThink Pro, these are the "chroma rings" and we are
looking down, on top of, the L* axis?
A Chroma value is given at the bottom of the target but what are the
two numbers at the top of the Neutral Rendering Chroma Target?
"Curves" shows the CMYK ink curves for neutral rendering and a fifth
element in the opposite direction displayed with a gradient, what is
this, is it L*? Does it show the gray ramp from media white point to
Dmax using all channels?
I would go so far as to say that the outer gamut boundary size isn't
all it's cracked up to be (or overrated). Even tonal distribution
and neutral stability I believe are more important than outright
color saturation.
I agree, this has been my experience too.
Who is to say that the first attempt was flawless, its just a
characterization? After all I'm the one making VISUAL evaluations
for ink bleed, pooling, paper cockle, etc. and then setting new ink
restrictions.
Visual evaluation for ink bleed, etc., is a good thing but I also
find that the neutral curves and chroma variation in CTPro are a
good evaluation if you have the right total ink limit or not.
BTW, what RIP are you using? I've got a "cheat sheet" I've made for
others that are specific to the ColorBurst RIP that you may find
helpful.
For Fine Art work I am using ColorBurst (clients location) and
StudioPrint (my location), and sometimes Onyx Production House for
commercial work, although I was disappointed with the results of Onyx
and the HP Z6100ps when using High Pass. We switched to the built-in
RIP for that printer.
Thank you very much for helping me expand my knowledge in these areas.
David Wollmann
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