Digital BW, The Print

Austin, you wrote:

> Yes, there is a MARKED difference in the results.  The "analog gain" that
> Nikon has merely shifts the tones up or down the "scale".  Example:
>
>         -
>       - - -   - -   - -
>     - - - - - - - - - - -
> 0 1 2 3 4 5 6 7 8 9101112131415
>
> now shift that up:
>
>           -
>         - - -   - -   - -
>       - - - - - - - - - - -
> 0 1 2 3 4 5 6 7 8 9101112131415
>
> Same curve, just different "values", but all relative values are
maintained.
> What it's useful for is getting your entire tonal range within the range
of
> the scanner...but other scanners do that as well with their exposure
> setting.
>
> If the scanner is designed such that it has actual analog gain between the
> CCD and A/D, you would EXPAND your analog data, and actually get MORE
tones:
>
>     - - -
>   - - - - -   - - -     - - -
> - - - - - - - - - - - - - - - -
> 0 1 2 3 4 5 6 7 8 9101112131415
>
> The limit, of course, is our vision (and noise in the CCD/analog
> circuitry/AD).  As long as you can get 256 tones out of your data, and you
> have tonal "separation" between tones you want to show tonal separation
> between...more tones in the image data wouldn't necessarily do you any
good.
> Again, I understand the Piezo driver claims to give more tones beyond what
> you give it for data, to smooth the tonal transitions.

I get the picture. But I doubt it will mean a difference in CCD filmscanners
with B&W films. Of course they shouldn't have called it analoge gain in the
Nikon software but if it really was analog gain it wouldn't be usable if
only for the softest, finest grained negatives. I'm using Polaroid 665
negatives and that film could be a candidate for it. Its compression is also
limited so one can only use it for contrasty scenes with some extra tricks,
pre-exposure etc.

The difference should be more pronounced in a PMT drumscanner with the
higher dynamic range. In a CCD scanner the analog data is the limiting
factor or it may just be equal to the B&W film densities, the limitation
isn't in the film. Expanding the analog data of a CCD scanner when it scans
reflective originals seems more appropriate. Colour negatives may have
enough compression to use analoge gain but there will be little left to
expand, maybe B&W films that are specially developed to keep a low contrast
and that have a grain fine enough to deliver that tonal separation. Slides
will all be beyond the range. In practice I doubt you can use true analog
gain on a CCD filmscanner, there's no margin left at both sides of the tonal
scale.

Ernst