Re: scanner profiling + w/b
Re: scanner profiling + w/b
- Subject: Re: scanner profiling + w/b
- From: email@hidden
- Date: Mon, 9 Jul 2001 10:40:16 EDT
In a message dated 7/9/01 7:17:04 AM, email@hidden writes:
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anybody please correct me if I'm wrong, but let me assume something. I
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think
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creating a scanner profile goes like this:
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1. there's the target with a number of fields who are designed to describe
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the gamut of the scanner.
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No the scanner doesn't have a gamut, more like a resonse curve... the media
has a gamut, and its the gamut of photo paper or film that is being defined
when you build the profile, so the results are not of much use for other
media.
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2. this target is to be measured by a spectro creating data which is
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dedicated to be the PCS.
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3. in order to create the profile the scanned RGB-values are assigned to
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the
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according LAB-values. That's what the LUTs are based on.
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With output profiles its the Lab to output correction table that is the
significant element of a profile, but for scanners a simple RGB to Lab table
is all you get...
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Maybe it's not that simple in particular, but basically I think that's
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it.
Close enough for the ideas you are dealing with here...
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So there's just this one direction (RGB->LAB), just this one LUT and there's
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no mapping, it's just called perceptual bacause it is the rendering default.
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Choosing any other intend in the convert to profile dialog makes no
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difference, because the other intents refer to perceptual/this one table.
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Thats about it...
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Now I have one question and I could imagine this has been discussed before,
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(if so it was before my time joining this list...) but in what situation
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is
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it best to set white/black? My current procedure gives acceptable results,
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but I would appreciate to hear about a better way.
Al long as you are using a highbit scanner you can set them in advance (if
your software will deliver targeted highbit to Photoshop) or afterwards (the
scan raw and correct in Photoshop method) and the results will be
indistinguishable. With old scanners that could only deliver 8 bits of data,
targeting in advance improved your quality by not losing levels to later
correction; now that is pretty much a moot point.
C. David Tobie
Design Cooperative
email@hidden