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[filmscanners] Re: over resolving scans



Laurie writes:

> I am not sure if I understand fully Anthony's
> comments on grain or alaising on true silver
> halide films being emphasized and more noticable
> with lower resolution scans than higher resolution
> scans.

At certain key scanning resolutions, which vary by film, exposure, etc.,
there is some interaction between the scan and the grain in the image that
may create the impression of larger or more obvious grain in the scan than
is actually present in the film.  If the resolution is held below this key
threshold, grain simply blurs out of existence (but detail does, too); if
the resolution is raised above this threshold, the interaction disappears
and grain starts to look as it would on an optical enlargement.

This seems to happen a little bit with Tri-X at 2700 dpi, although it's
really hard to tell.  It is rumored that this happens with Provia and Velvia
at much higher resolutions, which may be one reason why they seem to show
more grain in scans than they actually have in real life, but I've not been
able to isolate clear evidence of this myself.

> He may prefer the mushier grain appearace to
> the sharper more emphasized one; whereas others
> do not.

I actually prefer no grain at all, but few films have such fine grain that
it cannot be detected even in the highest-resolution scans.  Tech Pan is in
this category.  Also, interestingly, Portra 400BW and some other chromogenic
B&W films have incredibly fine grain, especially given their high speed;
400BW has grain that looks a lot like Tech Pan, at least at 4000 dpi or
below (that is, it appears to have practically no grain at all).  This has
persuaded me to shoot a lot of 400BW; I don't like the way it reacts to
light, but the absence of grain is great, and allows cropping and
considerable enlargement.  For a good example of how well this film can
perform under good conditions, see

http://www.smallevents.com/portra400.jpg

Scanned on the LS-8000ED at 4000 dpi, with ICE set to normal, no GEM or ROC,
single simple, superfine mode off, monochrome 14-bit output, all other
settings at default.  I used Photoshop to pull extra detail out of a couple
of the deepest shadows and brightest highlights (the detail was present in
the scans but didn't really show on the monitor without pulling them a bit
towards the midtones), and to downsample in steps to 1600 pixels wide with
intermediate USMs of 98, 0.7 pixels, 2 threshold.  The focus point was on
the central figure in the image, the one with the vest.

I'm anxious to try Portra 400BW in 6x6; my mouth waters at what that might
look like!

> Personally, I always scan at the maximum optical
> resolution that the scanner is capable of ...

So do I.  However, since I happen to have two scanners, with different
maximum resolutions, I try to use the 2700-dpi scanner for films with so
much grain that the 4000-dpi of the other scanner isn't justified, just to
ease wear and tear on the latter.

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