Scanner targets/Profiles
Scanner targets/Profiles
- Subject: Scanner targets/Profiles
- From: "Mike Eddington" <email@hidden>
- Date: Fri, 31 Oct 2003 16:13:00 -0500
I have scanner HCT 4x5 transparency targets for both Fujichrome and
Ektachrome material as well as an Ektachrome IT8. I use the profiles
created from them with the corresponding transparency material (Kodak
for Kodak...Fuji for Fuji). There are times when everything is
hunky-dory...the scans come out great. However, there are times when the
profiles just don't seem to represent the material I'm scanning very
well. Often scans will come out with a bluish or reddish cast. This has
happened with both Fuji and Kodak media (I'm referring to 4x5 film, not
35mm, and not kodachrome). I have tested my scanner for repeatabilty and
its rock solid (Hell 3800) and have had color consultants check out my
profiles....a-ok.
Numerous sources inform me that a scanner target made from the same
constituent dye sets as that of the material going to be scanned will
give the most accurate results and that a target such as the Q60 (IT8)
using Ektachrome material will represent the entire family of Ektachrome
dye sets. I'm trying real hard to believe this. I'm just wondering if
there are other factors that can come into play. Our transparencies
often come into our plant in batches from the photographer. Is it
possible that the conditions the film was processed in, or other factors
might change the characteristics of the film so that it is no longer
represented accurately by the profile? I certainly understand that color
adjustments may be needed and fully expect to make them, but rather
frequently I find that the adjustments need to be more aggressive than
they should be.
Another question...when viewing an RGB image with a CMYK proof
simulation in Photoshop 7, highlight detail often will visually drop
out, or a tone appears that does not match the numerical data displayed
in the info palette. Once the image is converted to the CMYK profile,
highlight detail can be viewed accurately. This occurs more dramatically
when using perceptual rendering, although this can be seen to some
degree using colorimetric intents. I understand that the perceptual
intent will compress the entire gamut in order to retain the
relationship between colors, but I can't explain why highlight detail is
not accurately viewed until the image is converted to the profile space.
Any comments?
mike
_______________
Michael Eddington
meddington@nac-mi.
_______________________________________________
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