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Re: [OM] Mea Culpa - & - Scanners

Subject: Re: [OM] Mea Culpa - & - Scanners
From: Ken Norton <ken@xxxxxxxxxxx>
Date: Sun, 5 Jan 2014 16:36:35 -0600
> Well, perhaps I should check focus more carefully.  Maybe that's why I
> didn't find more than 2400 dpi necessary. :-)

Hmm...



> Williams spends many pages describing the maximum resolutions attainable
> by amateur and professional photographers using unskilled and skilled
> hand held methods and low to high resolution films on up to heavy studio
> grade equipment with very high resolution B&W and extreme measures take
> to prevent vibration.  The average hand held photograph taken with
> typical color films of the day fares poorly with resolutions ranging
> from 20 lppm for the typical rank amateur to 30 lppm for the careful
> amateur to 40 lppm for the very careful and meticulous processional.
> It's actually rather disappointing since 40 lppm only translates to
> (80x24) = 1920 pixels vertically and (80x36) = 2880 pixels horizontally
> or about 5.5 megapixels for a 35mm film scan.  Is this perhaps where the
> 5 MP resolution of the E-1 comes from as "good enough"?  Of course, it
> probably takes 4000 dpi to actually resolve that 1920 pixels vertically.

And this is where the rub comes in. It's not how many line pairs per
mm there are in film, but where those line pairs are. What if those
lines aren't exactly parallel or perpendicular to the sampling
(scanning) technology? It takes much more scanner resolution to
effectively oversample the film in order to get an adequate
representation of what the film actually captured. I find that 4000
dpi is pretty close to that, but 5400 (Minolta) would be even better.


> Resolution of low contrast areas in typical
> color films only ranges from about 50 to 80 lines/mm and perhaps double
> that in high contrast areas.  No matter how good and stable the lens the
> end result can't be better than that and will likely be appreciably less.

This is highly dependent on the film. Fujichrome Provia 100F being
actually pretty bad in this regard. Velvia 100 (not F) is about the
best Fujichrome.

AG


-- 
Ken Norton
ken@xxxxxxxxxxx
http://www.zone-10.com
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