Re: Photoshop Gamut warning vs ColorThink
Re: Photoshop Gamut warning vs ColorThink
- Subject: Re: Photoshop Gamut warning vs ColorThink
- From: "dpascale" <email@hidden>
- Date: Thu, 21 Feb 2008 13:43:24 -0500
Like many who have answered, I also had reserves on Photoshop gamut warning.
I still have them, up to a point; however, I recently made (last night) the
following test:
Test:
1-Generate a L*a*b* file with patches with varying Hue, Lighness, and
Saturation. The patches are layed out in such a way that they look like
slices of a 3D L*a*b* volume. The measurements were made on two slices, one
in the reds, and one in the oranges.
2- Set the proof setup to a printer profile I did for a matte paper I use,
in Absolute-Col
3- Print the image with the printer profile in Absolute-Col.
4- I measured the printed patches and compared them to the file values.
Results:
A- I measured patches near the gamut limit as well as within the gamut. The
patches considered "In gamut" by Photoshop were very close to the nominal
values (within two CIEDE2000).
B- The patches considered "Out-of-gamut" ALL had larger errors. One
important note: the appearance of the out-of gamut colors did vary from one
patch to the other. For example, when comparing two out-of gamut patches,
with one having a higher saturation than the other, the two patches had
about the same saturation but different hue and lightness.
C- The "Out-of-gamut" patches very well matched the patches outside of a 3D
printer profile gamut (I did not do an exaustive analysis yet but it looks
good).
D- The Photoshop gamut warning is completely different in "Relative
colorimetric" (the gamut warning is the same with or without BPC), and does
not matches the measurements.
I thus have confidence for Abs-Col, where the clipping is "clean", but not
when the out-of gamut colors are mapped to fit into the destination gamut.
Danny Pascale
email@hidden
www.babelcolor.com
----- Original Message -----
From: "Mike Eddington" <email@hidden>
To: <email@hidden>
Sent: Thursday, February 21, 2008 10:39 AM
Subject: Photoshop Gamut warning vs ColorThink
This has been brought up on this list before, but I'm wondering if anyone
can add anything additional regarding Photoshop's gamut warning. Some
colors that do not trigger the gamut warning in Photoshop will plot
visibly outside the gamut in ColorThink Pro. So, for instance, if I want
to determine a group of Pantone colors that are within a particular gamut
(in this case Gracol2006_Coated1v2), I am not able to entirely trust the
Photoshop gamut warning. Can anyone offer some clarification on how
Photoshop is determining out of gamut colors. I confirmed the issue with
GMB's Profile Editor.
This is sort of a second question but does anyone know of a utility that
would allow plotting of a color list that will report the amount of
colors that are out of gamut?
Michael Eddington
QA Manager/G7 Certified Expert
North American Color, Inc.
www.nac-mi.com
www.nac1to1.com
www.photo360.com
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