[filmscanners] Re: My best scanner/film combinations

["" <anthony@ohalloran.co.uk>]

michael shaffer wrote:
>
> Austin writes ...
>
> > > > ...  Grain is a matter of resolution, not a
> > > > matter of tonality.
> > >
> > >   ...  Assume 2 films ... both the same speed and
> > > resolution, ...  To achive the same tonal range
> > > by scanning, you need to ask the scan of the negative to
> > > increase the contrast ... which will enhance the grain.
> >
> > Hi shAf,
> >
> > Certainly not if the scanner can't resolve the grain...  The increase in
> > density range is handled by exposure time.  Nothing in the CCD-A/D path
> > changes...just the time the light shines.  The light type the scanner uses
> > also has a huge effect on grain, scratches etc.
>
>   I would agree to dissagree on that point.  That is, if you do anything to
> stretch a film's D=2.5 to an equivelent 3.0, you'll enhance the grain ...
> whether it's more light or a longer exposure time.

This is what I think you are saying.....
When you stretch a film's D=2.5 to 3.0 you are increasing the contrast.
As the contrast between neighbouring grains/dye clouds increases they
become more prominent thus the perception of a grainer image.

Think of it this way......
If i do a scan of a slide and a neg (both 100 speed film) using the
scanner at full dynamical range I get 2 scans with the same grain
appearance.  I have to increase the contrast on the neg image so it
looks good for printing. This increases the contrast in neighbouring
pixels which draws more attention to what people on this mailing list
call grain. The grain does not get bigger i.e. you are not losing
spatial resolution. Effectively there is less useful colour information
in this scan now.
Going back to the slide image, you do not have to do the increase in
contrast so you do not have this problem.

Anthony

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