You've got part of it, Wayne. If I'm correctly recalling Ctein's theory,
during the traditional enlargement process film grain is spread across the
silver halide on the paper in such a way that it has the effect of
resampling. (If this is incorrect, blame me, not Ctein, for fumbling!)
The other part has to do with alignment of the scanner's light source. When
in such close proximity to the film if the light is even slightly off-axis
it will accentuate grain.
The easiest way to demonstrate this is to pick up a Kodachrome or any 400
chrome with some blue sky and hold it up to a painfully bright light source
like a frosted 100 watt bulb (not next to the bulb - step back a few feet!).
Tilt the slide very slightly top-to-bottom and side-to-side as you look
through it. You should see some alarmingly chunky grain in the blue sky.
This is most apparent in Kodachrome due to the nature of its emulsion.
But the grain doesn't show up to such an alarming degree in silver halide
prints.
Regarding resampling, I typically downsample from huge files whenever I want
a quality scan to upload to the web. For whatever reason our flatbed
scanners deliver better results when I scan prints at 200-300 ppi, do all my
Photo-Paint work on the large scan, then downsample to the desired onscreen
viewing size *in pixels*. I don't change the original scan resolution from
300 ppi to 96 ppi.
I'm guessing the reason this method delivers better results for me is
because the cheapo flatbed/TWAIN driver's inferiority complex can be offset
by Corel Photo-Paint's overwhelming power.
-----------
Lex Jenkins
----------------------------------------------------------------------
"Budda-budda-budda!!!" - Sgt. Rock
======================================================================
From: Wayne Shumaker <shumaker@xxxxxxxxxxxxxxx>
Date: Wed, 25 Oct 2000 10:28:54 -0400
I know my own experience with scanning Provia F versus 400 print film
(LS-2000 scanner) that the grain in the 400 print film gets accentuated
by the scanning process much more than the Provia, and the grain seems
to "blend" better with normal film processing. I think this is partly
related to the small sampling aperture of the scanner, possibly causing
aliasing effects. (aliasing is where higher frequency sampled data
"aliases" down to a lower frequency. In this case, frequency is the
spatial frequency.) With the LS-2000, using the CleanImage feature with
multi-sampling can sometimes help; I think it filters the data, sort of
like an anti-alias filter. Also this may be one of the reasons for the
recommendation that you sample at the highest and then down sample
later in photoshop.
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