[filmscanners] scanning at less than optical res

["Bob Frost" <bob@frost.name>]

Is this correct?


"As I understand things, a scanner with an
optical resolution of 4800dpi can take a sample reading every 1/4800 of an
inch. If you scan at the optical resolution, that is what is does and you
get 4800 readings per inch along that axis (usually a different resolution
on the other axis).

If you scan at 1200dpi, the scanner usually either samples all the 4800
possible data points per inch and throws three out of every four away, or
only samples every fourth possible point. So you are only getting one
quarter of the possible data from the film. So why scan at large format if
you are throwing three quarters of the film data away?

With Vuescan software, you can set it to scan all 4800 data points per inch,
but then to take the average of every four data points and reduce them to
one, so that the file you get out is the equivalent of a 1200dpi scan, but
all the data points have contributed to the final result."

Bob Frost.

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