Re: Photoshop Gamut warning vs ColorThink
Re: Photoshop Gamut warning vs ColorThink
- Subject: Re: Photoshop Gamut warning vs ColorThink
- From: Chris Cox <email@hidden>
- Date: Wed, 27 Feb 2008 10:00:03 -0800
- Thread-topic: Photoshop Gamut warning vs ColorThink
I picked an example that would clearly explain the issue to people who
aren't familiar with how ICC profiles are constructed or specified. A less
extreme example would have had people debating deltaE tolerances for weeks
instead of understanding the problem behind the example.
If you try to map all colors (all of the allowed LAB values) into a target
gamut, you will require extreme desaturization and usually quite a bit of
contrast reduction. Perceptual intents do NOT map all colors into the
target gamut - they map some reference gamut (say, sRGB) into the target
gamut and (usually) try to provide some smooth falloff near the gamut edges.
Anything outside the reference gamut is still likely to be clipped in the
output.
Yes, the ICC has figured a few things out -- which is why the V4 perceptual
intent specifies a reference gamut instead of maintaining the fiction that
perceptual intent would map all of LAB into the target gamut.
> Date: Wed, 27 Feb 2008 00:57:58 -0500
> From: email@hidden
>
>> Chris Cox writes on Tue, 26 Feb 2008 19:27:24 -0800
>> Do you have a profile that maps all of LAB into a newsprint gamut and
>> doesn't clip anything or look crappy? If so, many newspaper publishers
>> would like to talk to you....
>
>> On 2/26/08 6:05 PM, "Roger Breton" <email@hidden> wrote:
>>>> No, because perceptual intent cannot map all colors into gamut without
>>>> extreme (ugly) compression.
>>>
>>> That's a debatable generalization, Mr. Cox. Not all perceptual intents
> are
>>> built the same. This bein said, that doesn't take any value away from
>>> Photoshop's Gamut Warning.
>>>
>>> Roger Breton
>
> I think your response confirms Roger's comment - you specifically picked
> the most difficult print medium. Any Profiling App is challenged by the low
> dynamic range and small chromatic gamut extent of newsprint. But in
> general (the word Roger used), for devices with reasonable gamuts, profiles
> can do a good rendering of images. Afterall the ICC has been around for 15
> yrs now which is enough time to have figured a few things out.
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