Re: mapping extreme colours perceptually [not]
Re: mapping extreme colours perceptually [not]
- Subject: Re: mapping extreme colours perceptually [not]
- From: neilB <email@hidden>
- Date: Sat, 25 Aug 2001 18:57:52 +0000
Thomas
thanks for the mail
my bad English is showing me up
On 25/8/01 at 10:13 am, email@hidden (Thomas Knoll) wrote:
>
>> So how is perceptual intent *really* implemented? Answer: the author
>
>> of the profile building tool makes some wild guess of a "typical"
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>> source gamut,
>
>is he effectively anticipating the PCS extremes here?
actually what I meant by this was - is he anticipating the
extremes of source image data as seen within the PCS. I guess the
answer is yes?
>
>
No. In fact the relevant gamut is that of the unknown source *image*
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(not even the source color *space*).
OK
>
The PCS gamut is huge, much larger in fact than the gamut of
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the real world.
>
>
> > and builds some fixed desaturation and darkening (of
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>> high saturation colors) into the destination profile.
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>similar to Perceptual, then, in colours outside of the expected
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>data range?
>
>
Even for colors inside the expected gamut, it often looks better to clip them.
in my example extremely saturated blues [UltraMarine] are printing
as solid [no detail ] areas in spme parts, plus the printed colour
is blue black - not dark saturated blue as in the original. This
with [Colormatch > Epson 7000 / Lyson Fotonic inks/Lyson StdArt
paper] profiles from Both Gretag and Kodak.
I've seen this as blocking of colours in green foliage too -
detail is gone and ink goes on solid in areas - like really bad
perceptual mapping.
>
Selecting out of gamut colors is useless anyway, since it adjusts
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only them, but not nearby colors, resulting in hard edges in the
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result.
>
>
A better solution is to turn on gamut warnings and use the
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hue/saturation command. Gamut warnings with RGB spaces are fully
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supported in Photoshop 6.
As to using a selection to restrict desaturation to out of gamut
areas, do you not approve of this even if the selection is
feathered?
How about the sponge tool / desaturate?
thanks again Thomas
neil
Neil Barstow