A few scanning tips

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Dust and Scratches

Dust and scratches are a much bigger problem when scanning film. The resolution is high, and it really shows well. Film is very fragile, and scratches and oily fingerprints are a risk and concern. Professionals often wear white lint free cotton gloves when handling any film, and such disposable gloves are available at photo supply stores. Keep your fingers off the film surface.

Don't just throw your film in the drawer. Don't leave it laying out uncovered. Treat the film as if it were irreplaceable. The photo supply stores have archival protectors, inexpensive clear polyethylene sheets with filmstrip pockets of all sizes, to hold a roll per sheet, which you can store as pages in a notebook. There are many brands and sizes and choices, and they are handy and safe.

Kodak film processing typically returns negative film enclosed in a special protector. The film strip has clear thin cellophane-like covering both sides of it, glued at the perforations, with a paper re-order form along one edge. You can't scan the film without removing it, and would not want to, but with a little care, it just peels off each side. Don't get fingerprints on the film when doing this. Practice first on an unwanted filmstrip. Then protect the file strips in some other way.

Dust is a difficult problem, at least on my workbench. Commercial shops use filtered oil-free air compressors located elsewhere, and pipe the low pressure air to each work station. Expensive and noisy, and I am very envious.

I don't know what to tell you about cans of compressed air, but I don't use them on film. If you do, never shake the can. If the can has been shaken, or if the can is not held vertical, some Dichlorodifluoromethane propellant may be released with the air, resulting in a residue adhering to the film. This residue can be removed with a film cleaner (Edwal or PEC-12, etc) and a lint free cloth. But it makes an easy job difficult.

I would suggest a clean soft camel's hair brush to carefully brush the dust from the film before putting it in the film holder. The film holder creates corners to hold the dust, and the brush is more effective before that. The photo supply store has nice brushes, one inch wide for film. Some film brushes have a squeeze bulb to also blow a little air, and some have anti-static elements. But if you first brush the brush tip on clean plastic, like the film holder or the back of a calculator case, it creates a small static charge that lifts the dust off. Do guard your film brush as the most valuable and fragile thing you own. NEVER touch the bristles with your oily fingers or skin. Carefully protect the brush, including while in storage.

The Clone Tool is the standard way to retouch spots in the image, see chapter 22.

There are software filters that attempt to filter out dust and scratches. Photoshop has a Dust & Scratches filter with parameters rather like an Unsharp filter, but in reverse (see its Help file).

A few film scanners have a hardware infrared sensor, four channels of CCD for Red, Green, Blue and an IR image. The IR channel is used by software like Digital ICETM and VueScan to detect and remove dust, fingerprints, scratches, and other film damage. This scanned IR image is used as a mask to localize the blurring effect to only the problem area. Anything the IR sees is not a normal color component, and so the entire film area is not softened, the IR mask allows just the bad spots to be treated. Still, all of these methods are basically blurring actions, which soften the image. Resharpening goes a long way towards recovery, but it's always better to eliminate the problem before it happens.

The Infrared channel does not work with B&W film because the silver content blocks all light equally. Kodachrome dyes are partially visible in infrared too, but all other color film works well with IR dust and scratch software.


Copyright © 2000-2010 by Wayne Fulton - All rights are reserved.

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