Re: Photoshop Gamut warning vs ColorThink
Re: Photoshop Gamut warning vs ColorThink
- Subject: Re: Photoshop Gamut warning vs ColorThink
- From: "dpascale" <email@hidden>
- Date: Wed, 27 Feb 2008 11:11:53 -0500
Mark,
I did a comparison of the Photoshop gamut warning vs Argyll xicclu utility.
In essence, the Argyll utility flags all clippings with a DeltaE number.
The comparison shows that the Photoshop warning kicks in between 5 and 8
Delta-E, as determined by xicclu, depending on colors. Please note that the
xicclu values are not to be considered as references at this moment, but
they are "hard" numbers used for comparison. This test was done for one
particular printer profile, with Abs-Col Rendering Intent. These values are
in line with your 5 Delta-E assesment, but they extend it in a region where
I feel uneasy.
What I need to do next is a detailed comparison between the Photoshop
clipping flag, the Argyll xicclu values, and what is measured. So, at the
moment, I cannot say which one (Photoshop or xicclu) is closer to "reality"
(on average!), with reality being the printed result, which needs to be done
with a fresh calibration, controlled conditions, etc.
Danny
email@hidden
----- Original Message -----
From: "Mark McCormick-Goodhart" <email@hidden>
To: <email@hidden>
Sent: Wednesday, February 27, 2008 10:49 AM
Subject: Re: Photoshop Gamut warning vs ColorThink
Chris, you have convinced me. After trying to figure out the best way to
describe the Gamut warning tool, I have reconsidered, and conclude "gamut
warning" is indeed an apt description of this feature. For those who
prefer "clipping limit" that seems like a good description, too. I still
believe that the Gamut warning is apparently being calculated on the
basis of about 5dE between the source color (ie., the color after all
image edits, profile mapping intents, and BPC have been applied) and the
predicted output color. Chris, or someone at Adobe, I'd very much
appreciate a better understanding of how gamut warning calculates the
comparison if you think I'm wrong about my 5dE assessment of this tool's
clipping limit criterion.
With all due respect to those who don't find gamut warning overlays
useful in light of their ability to visualize print output via
softproofing, I agree with Chris that the gamut warning is more useful
today than ever. Why? Because many folks are moving to larger and larger
working spaces. Prophoto seems to be getting recommended to
photographers a lot, lately. Because no monitor exists that can display
the wide gamut of such a working space and worse yet, some colors are
imaginary, I find it very useful to have an overlay that guides me to the
color clipping transition of the printer output rather than the apparent
clipping that is being caused by the monitor profile. That said, I even
find it instructive to teach students about the monitor or working space
color gamut by taking the AaI_LAB_HueSlice_Image.psd target I described
in an earlier post and choosing the appropriate working colorspace or
monitor profiles to examine. Because this LAB image file is in fact an
image that can throw the whole LAB encoded colorspace at the output
device, it is also helpful to evaluate how and where the "secret sauce"
of perceptual mapping intents quit attempting to compress colors after a
given chroma value is reached. Gamut warning very nicely locates that
transition. Softproofing alone may or may not reveal them depending on
the confounded aspects of rendering to a gamut constrained monitor.
Chris Cox wrote:
Message: 3
Date: Tue, 26 Feb 2008 18:03:07 -0800
From: Chris Cox <email@hidden>
Subject: Re: Photoshop Gamut warning vs ColorThink
To: Andrew Rodney <email@hidden>,
<email@hidden>
Message-ID: <C3EA04DB.68481Ìemail@hidden>
Content-Type: text/plain; charset="US-ASCII"
It tells you what parts of your image are out of gamut.
Otherwise, how would you know what parts of the image need to be brought
into gamut?
A proof setup tells you how the image will look, but unless you have a
really good display AND really good eyes, you aren't likely to tell
which
areas have been clipped.
The gamut warning is probably more useful today than when it was first
implemented - now we have more accurate color transforms, and more
accurate
color data.
_______________________________________________
Do not post admin requests to the list. They will be ignored.
Colorsync-users mailing list (email@hidden)
Help/Unsubscribe/Update your Subscription:
This email sent to email@hidden
_______________________________________________
Do not post admin requests to the list. They will be ignored.
Colorsync-users mailing list (email@hidden)
Help/Unsubscribe/Update your Subscription:
This email sent to email@hidden