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[filmscanners] Re: Advice on scanner settings



"Arthur Entlich" wrote "Both methods (printing and looking) are too
subjective for my taste in regard to this issue.  I'd really like to see a
objective map of the changes.  My personal  sense is that jpeg is much
better than most people give it credit for.
----------------------------------

When I posted my comments to your earlier question, the "make a print"
wasn't addressed to you. I was pretty sure you were aware of that
possibility. I share your opinion that jpeg is much maligned and is a much
better file format than most people believe.

My broader point is that we can get tied up in technological details and
completely miss the big picture. One of the issues we almost never talk
about is the "quality" of pixels in a scan. There is a significant
difference in the scans from a desktop scanner and those from a high-end
professional scanner like an Eversmart. The raw scans may look similar, but
if the images require huge color-correction moves, the high-end scan will
probably end up looking better.

I suspect that most of the members on this group are interested in personal
scanning, though there are no doubt some who are professional photographers
dealing with high quality images. OTOH, I doubt National Geographic uses a
desktop unit for their scans. Since we are starting with something less than
perfect scans, I don't know that trying to isolate the smallest levels of
file "damage" is a profitable path to take. I *do* believe that a
subjective, visual test is the appropriate measure for us to evaluate what
we do to our files.

I believe you can save jpegs at level 6 without ANY visual damage to a file
(except by examining at the magnification of 200+% pixel-for-pixel, which is
almost never done with real-world images). This will save an order of
magnitude of disk space over tiff files: for the typical 4000ppi scan, this
will yield 1.5-meg files rather than 40-meg files, a reduction of almost
95%. I think this is a worthwhile savings.

Did you try flattening the black image and checking levels? When I tried it
with a level 12 jpeg, all the pixels were crammed over to the left (0) end
or the histogram. It looked like the largest value was maybe 6.When I tried
it with a level 6 jpeg there was a wider range of values, but there seemed
to be only a few pixels grater than 20 or so. Sliding the mid-point arrow in
Levels to the left to open up the black file and make a visible image, an
then using the point-source eye-dropper to check pixel values, the lightest
I could find were at maybe 15 value. I think this shows that the jpeg is
"different" from the tiff, but I don't believe that mean it is worse. If you
can't see a difference, is there one?

Preston Earle
PEarle@triad.rr.com
www.sawdustforbrains.blogspot.com

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