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Better Scanning Techniques

How to squeeze the utmost quality out of your film/scanner combination.

By Tom Ang

Of the fundamentally different methods of scanning, making a scan from a reflection original-such as a print-is far easier than scanning a transmissive original, such as a transparency or negative.

For scanning reflection originals, the dynamic range that has to be encompassed by the scanner is modest: less than six stops (i.e., the difference between darkest and lightest is six stops). For transmissive originals, however, the dynamic range can be wide indeed, running to 11 stops or greater.

This is important for two reasons. First, it is extremely difficult to arrange lighting and optics that can penetrate the highest densities seen in modern films. Second, the long dynamic range makes heavy demands on the computer coding required. As a result, very inexpensive flatbed scanners can make superb reflection scans, whereas to obtain really good transmission scans you need relatively costly hardware.

Squeezing the utmost quality out of your film/scanner combination is simple to effect, but it costs in increased scanning time. If you are fortunate enough to be throwing away an old computer, see if it can still run the scanner (and printer too). Keep it, and forget about tying up your main computer. It is here that Apple Macs come into their own: One inexpensive cable is all you need to network two Macs together.

Scanning strategies
Modern scanners produce surprisingly good results. But a number of strategies can help you obtain the best-quality from whatever equipment you use.

Scanning in 48 bit: A number of modern scanners will scan into 16 bits per channel, i.e., 48-bit space (some into 36-bit space or 12 bits per channel). This is necessary in order to code for high maximum-density readings. Some will produce 48-bit files, while others only output files in 24 bit. If you have a choice, retain the scan in 48 bit. This, despite the overheads in terms of longer scan and larger files, is well worth doing for color transparency materials. Ensure you carry out color and tonal corrections while still in 48 bit. Unfortunately, even superior software such as Equilibrium’s DeBabelizer does not work in 48 bit, but most of the basic corrections are available in Adobe Photoshop and Corel Photo-Paint 10. Binuscan’s PhotoRetouch works fully in 48 bit. Once the basic corrections are done, you can (and indeed should) turn the image into 24 bit.


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