Re: [Leica] scanning Leica slides vs colorneg

["Henning J. Wulff" <henningw@archiphoto.com>]

At 5:34 PM -0700 9/27/99, Godfrey DiGiorgi wrote:
>> It is my understanding that your typical scanner is really not up to
>> snuff to slides and does better with ColorNeg while a Polaroid 4000
>> can deal with slides fine. By the end of the year who knows the
>> options but can anyone confirm this or know much about it?
>
>Transparencies, being positive images, have more dynamic range than
>negatives (the materials are not sensitive purely linearly, the response
>curves are better characterized as partial differential equations of order
>2 - the useful range of exposure tends to happen in the toe and linear
>section of the curve, each transfer from negative to positive includes a
>rise in contrast just like making slide duplicates includes a rise in
>contrast). What limits scanning of transparencies is similar to what
>limits making good prints from transparencies: the contrast gain of a
>slide which has just too much dynamic range burns highs and loses lows.
>
>Given this, the limiting factor in how well you can scan a transparency or
>negative has to do with the scanner's bits per channel which relates to
>its DMax capabilities (as well as all the other details of quality
>alignment, good focus, etc). Shooting transparencies for scanning is much
>like shooting them for printing: you have to be careful to keep the
>significant portions of the slide to a tight lighting ratio not only to
>keep within the transparency material's exposure tolerance but also to
>minimize contrast gain. A 12 bit per channel scanner at 2700 dpi will do
>quite a good job with slides where a 10 bit handles only the better
>exposed slides well, and an 8 bit unit's capabilities are rather limited.
>Most negatives scan very well even with 8 bit units, although 10-12 bit
>units do seem to wring more brilliance out if properly calibrated and
>adjusted for the film. Part of this might be that the more expensive
>scanners generally get better software as well, part of a professional
>package.
>
>Added dpi resolution surely helps no matter what but the limitations here
>are more related to how much detail your digital image will have at what
>enlargement size rather than how well it will reproduce the color/tonal
>scale. A 2700 dpi film scanner, calibrated properly, will return enough
>pixels to make a quality 12x-16x enlargement from 35mm format (16x is
>about 170 ppi, 12x is a healthy 225 ppi). While this doesn't beat the top
>notch printing technology available today, it's adequate for most people's
>home uses. Going to 4000 dpi gives you closer to the drum scanner
>resolution capabilities if you want really large prints.
>
>Something must also be said for the fact that some scanners and their
>drivers are better optimized for transparencies vs negatives and vice
>versa. Part of the reason I chose the Polaroid Sprintscan 35E/S (10bit,
>2700 dpi, built-in DSP) was that in testing it, it seemed to be much
>better at rendering color negatives than the comparably price Nikon
>scanner was in 1996, the Nikon at the same price was better at rendering
>slides.


The present Nikon LS-2000, intrinsically, and enhanced because of its
multisampling capability does a better job of producing a decent slide scan
due to its lower shadow noise than the Polaroid 4000, as I mentioned in a
comparative report a while back. The extra detail available with the
Polaroid is not enough to compensate for its bad software and more limited
dynamic range. The LS-2000 is still a better value if your interest is in
slide scanning.

Adveritised Dmax and dynamic range capabilty are generally nowhere near the
truth, and dpi capability is also generally less. Caveat emptor!

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   *            Henning J. Wulff
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