Re: Clipping when converting from scanner space
Re: Clipping when converting from scanner space
- Subject: Re: Clipping when converting from scanner space
- From: Roger Breton <email@hidden>
- Date: Tue, 05 Apr 2005 10:13:07 -0400
> <Each of these conversions results in clipping of the histogram at each end,
> most notibly at the black end.
> It does not seem to matter if the rendering Intent is changed to perceptual or
> if Black Point Compensation is switched on or off.>
>
> I would think this would simply be a result of the mapping from the gamut of
> the scanner to that of the working space. Even with a larger space such as
> ProPhoto, there is likely data that needs to be mapped from the scanner space,
> and that would alter your histogram, no?
>
> <Try converting to Lab instead from your custom scanner profile. I know it
> does not sound logical but please give it a try. Converting to Lab should
> not get you any clipping, IMO.>
>
> You shouldn¹t get any clipping, but your histogram will certainly change as
> it¹s now based on Lab instead of RGB.
>
> <Once you got your image in Lab in Photoshop, try converting it to RGB,
> RelCol, and see if you
> still get any clipping.>
>
> This would get you identical results to that of converting directly to the
> working space would it not?
If it does, mike, that means that your above statement is on the money and
the redistribution of the histogram is just a natural part of the
conversion. Now, a better question, IMO, would be for Lee to compare his
custom scanner profile in 3D to his choice of RGB working space to see
whether the gamut clipping is visible there. If it is then, logically, the
choice RGB working space should be iterated until he finds ne that does NOT
result in any clipping.
Roger Breton | Laval, Canada | email@hidden
http://pages.infinit.net/graxx
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