This sounds like grain aliasing. The mathematics of this are rather complex
because it involves the MTF of the scanner spot and lens, the line spacing
of the scanner, and the grain size distribution of the film being scanned.
It occurs when the grain size is small enought that it exceeds the Nyquist
limit of the sampling process. It results in the high frequency portions of
the grain being duplicated as lower frequency noise, and adds to the normal
low frequency component of the granularity. The result is an apparent
increase in granularity.

There are only two solutions to this that I know of. The first is to
introduce an anti-aliasing filter in the optical path of the scanner. This
almost has to be done by the manufacturer of the scanner, as it must be
carefully matched to the MTF of the spot and optics. The second solution is
to scan with a higher lpi and a smaller spot size (and better lens MTF). If
that can be done with the scanner that you are currently using, you're in
business. Otherwise, you will need to find a scanner that can handle film
with the small grain size that you have.

Don



"Jytzel" wrote in message
m...
I sent some negatives and slides to drum scan to have the operator
claim that negatives show more grain in the final scan than slides. I
used 6x6 Fuji NPS 160, a film has low granularity rating. The other
film I used was E100G slide film. I find it hard to believe the
operator's claim. It seems that he is doing something wrong. What
could it be and how to get the best scan out of my negatives?
By the way, they use Crosfield drum scanners.

thanks
J