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Re: [OM] Scanning quality

Subject: Re: [OM] Scanning quality
From: "Peter A. Klein" <pklein@xxxxxxxxxx>
Date: Fri, 07 Dec 2001 11:50:03 -0800
Henrik:  Having used both methods, I agree with Tom's asessment.

However, there is one drawback to film scanning if you use fast film, especially fast black-and-white film. It's called "grain aliasing." The sliver grains are big enough that there is an interference pattern between the grain and the pixels. So you can end up with a picture that looks grainier than a silver print of the same size. If you zoom in on the original scanned image, you will see that small groups of pixels are alternating light and dark, making digital "grain" that is bigger than the silver grains were.

In that case, you might get a better scan with a silver print, provided that it was a good quality print made with a good enlarging lens, and the silver print was about the same size or larger than your target digital print.

Another solution is chromagenic B&W film, such as the to-be-discontinued Kodak T400CN and its successor, Portra 400 B&W. It uses dye clouds like color film, not silver grains, and scans much more smoothly.

All this said, there are grain filters in some scanning and image editing programs that can minimize this effect, often with little degradation of the image. Here are some examples of Tri-X negatives I took in the 70s, when Tri-X was probably a bit grainier than it is now. I recently scanned these with a Nikon LS-2000 (2700 dpi) and Viewscan, with Viewscan's grain reduction on "light," the lowest setting.

http://www.2alpha.com/~pklein/oldpics/framer.htm
http://www.2alpha.com/~pklein/oldpics/greasept3.htm
http://www.2alpha.com/~pklein/oldpics/homeless72.htm
http://www.2alpha.com/~pklein/oldpics/sorcerers.htm

Compare these to Portra 400 B&W pictures, with grain reduction turned off:

http://www.2alpha.com/~pklein/currentpics/mischa_emphatic.htm
http://www.2alpha.com/~pklein/currentpics/yulia_skeptical.htm

Aside from the grain aliasing issue, I agree with Tom: Film scanning is much better.

--Peter Klein
Seattle, WA


Tom Scales sez:

The difference is HUGE.

The 4000dpi filmescanners, in 16-bit mode, generate a 120MB Tiff file, at
approximately 5500x3500 pixels.  The flatbed might generate files that big,
but the results are limited by the print -- to a much lower quality.

More discussion is beyond this list, but to reinforce and summarize.

The film scanner is better. Much better.

Tom

> Do you who have the experience notice a HUGE difference between
> scanned prints and scanned negatives? Or is the difference
> "neglectable"?
>
> Henrik Dahl
>


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