Digital BW, The Print

>What is a good way to fine the proper focus for scanning on a
3200?

Sean<

I've made a spiral staircase of strips of slide glass 0.85 mm
thick and on each step a brush stroke of grainy ink with some
scratches through it. One side of the staircase starts at 0 mm
and when turned over there's a 0.45 mm step first. So I can test
the sharpness per 0.40/0.45 mm step. Best focus is approximately
at 1.7 mm with my 3200. Others have found other distances from
the glass bed.

The scanner has three planes where it should be more or less in
focus. At the glass bed for reflective scanning, at 1 mm for the
filmholder and at almost 3 mm for objects larger than the
scannerbed (for reflective scanning again). Ideally it should be
in best focus on the film at 1 mm and the DOF of almost 3 mm
should take care of the reflective scans that normally are not
scanned higher than at 600 ppi. I guess Epson thinks that the DOF
will take care of the shifts in production tolerance as the
actual focus can be higher or lower than the 1 mm above the
glass. Finding the better focus isn't a dramatic quality increase
but it helps especially when the scan is improved in Phothoshop
later on. Even more important is the planerity that I get by wet
mounting the film.

See Norman Koren's pages for the focusing measurements.

Ernst