RE: scanner profiles
RE: scanner profiles
- Subject: RE: scanner profiles
- From: "CS Carl Stawicki (4211)" <email@hidden>
- Date: Tue, 25 Feb 2003 09:22:45 -0500
I have a tiny 16x16 pixel RGB file that has all the neutral tones from 0-255
(one tone per pixel). I assign my new scanner profile to it, convert to Lab,
and check out the histogram. This shows me how the values get distributed in
the 'L' channel, and how many I loose. So the more evenly the neutral values
are distributed, and the less I loose, the better the scanner profile. The
'a-b' channels tell me how neutral, or not, the profile is. As far as
banding goes, if any part of the 'L' histogram shows a few spikes with a lot
of space between them, that indicates banding.
You could also convert this file from scanner to working space, and analyze
it the same way. (On a side note, this is one of the tests I performed to
learn about the advantages of a working space gamma of 2.2, versus something
lower.)
I also do visual tests alongside this. I scan a GATF photo (the fruit) at
the same time as the target and use it for visual analyzation. The numeric
evaluation explained above usually concurs with what this shows me, if a
problem (such as banding) is obvious enough.
If anyone's interested, I can email the 16x16px file to them to save them
the trouble of making it (it's pretty tedious). It's only a 1k tiff.
Carl.
email@hidden
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From: Tyler Boley
>
Sent: Monday, February 24, 2003 9:29 PM
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To: email@hidden
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Subject: scanner profiles
>
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I am finding it difficult to objectively evaluate scanner profiles. I
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have a few IT8's w/ ref files, and a few methods of profile creation.
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They all give slightly different results. Other than subjective
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comparisons between transparencies and scans displayed on monitor, is
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there some more objective way to evaluate the profiles' quality?
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Looking at them in Colorthink is fun, but well, just fun.
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Beyond accuracy, my main problem is color banding.
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Thank you,
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Tyler
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