Re: Epson No Color Adjustment Experiment
Re: Epson No Color Adjustment Experiment
- Subject: Re: Epson No Color Adjustment Experiment
- From: Rick Gordon <email@hidden>
- Date: Mon, 22 Dec 2003 01:27:44 -0800
On 12/21/03 at 2:06 PM -0500, email@hidden wrote in a message entitled
"Re: Epson No Color Adjustment Experiment":
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In a message dated 12/20/03 7:29:52 PM, email@hidden writes:
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>1) If the output were assigned to the false, higher-gamut version of Generic RGB somewhere in the workflow (as was the case in the second print), why would the results show less, rather than more saturation?
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This would tend to indicate a profile conversion rather than a profile assignment, which would make the colors brighter instead.
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Yes, I think it would.
I ran a test print of the same image converted to Wide Gamut RGB from Adobe RGB and then reapplying Adobe RGB profile, using the standard, unmanipulated workflow to see if in fact there might be a match (or near match) to the result of the print (call it print #2) that was printed the original file while the false Generic RGB (actually Wide Gamut RGB) was installed.
In fact, the results were only about half as desaturated as print #2.
So I'm just trying to get my head around what the actual set of transforms might be. I figure that some factor of the difference between Generic RGB and Wide Gamut RGB would be in there.
So might the set of transforms be something like this?:
1) The file begins as Adobe RGB or Untagged RGB interpreted through the default Adobe RGB working space.
2) Photoshop converts the Adobe RGB data to my custom printer/paper profile and sends it on to the print engine.
3) ColorSync grabs the data and converts the data to Generic RGB, and then sends that RGB data to the Epson driver, which being set for No Color Adjustment passes the data without further transforms into the portion of the print engine that translates the data into printer codes.
If that is the case, one expectation would be that passing the same data though the same printer using the same custom printer profile via a Windows box using the Windows Epson driver might produce a distinctly different result. Does it? In the case of the Epson "black box" printer/paper profiles, perhaps the variance is worked out within the "black box".
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At 4:05 PM -0800 12/20/03, Rick Gordon wrote in a message entitled
"Epson No Color Adjustment Experiment":
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I've demonstrated to myself the Generic RGB profile is definitely a factor when printing through the Epson Driver in Jaguar. I ran side-by-side prints using Photoshop color management for printing, setting my custom printer/paper profile and choosing No Color Adjustment. One print was printed as with the usual Generic RGB.icc in /System/Library/Color/Sync/Profiles; the other was printed after I swapped in and renamed Wide Gamut RGB to Generic RGB.icc.
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The print printed while the false copy of Generic RGB was installed was dramatically reduced in saturation.
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So this leads me to several questions:
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1) If the output were assigned to the false, higher-gamut version of Generic RGB somewhere in the workflow (as was the case in the second print), why would the results show less, rather than more saturation?
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2) What is the real impact of this for printing testcharts and creating printer profiles? If the testcharts are printed after interacting with Generic RGB, and the results are subsequently profiled, would the resulting profile data be substantially different, or would it be essentially the same, since in either case the workflow is consistent. Which I guess really means: In what way does the definition of Generic RGB impact the gamut, tonal range, and linearity of the testchart (or any other print)?
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___________________________________________________
RICK GORDON
EMERALD VALLEY GRAPHICS AND CONSULTING
___________________________________________________
EMAIL: email@hidden
PHONE: 415-663-8652
WWW:
http://www.shelterpub.com
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