I am currently scanning my 8x10 negatives at 1333dpi on a Howtek 4000
drum scanner resulting in a 120 MB image file. 1333 dpi is one of the
Howtek's "native resolutions; non-native resolutions, 1200 dpi for
instance, would require some interpolation.
The image area of my 8x10 negative is actually 7.625" x 9.625". My plan
is to produce final prints which are 16x20 resulting in a final print
resolution of 635 dpi. In my testing I have found that 600 dpi is
*significantly* better than 300 dpi. 1200 dpi is better still but just
very slightly -- certainly not worth the extra file size. Also, 600 dpi -
actual, is significantly better than the 600 dpi interpolated from 300 dpi
which Mr. Burkholder advocates.
I have had problems using diffusion dither bitmaps. They seem to yield
"gritty" or "grainy" prints in large monotone areas such as the sky or
calm ocean. On the suggestion of several readers of this list I tried
using a halftone linescreen. I used a 300 lpi elliptical dot
linescreen. Early test results are quite promising. The 300 lpi screen
(which is the highest my service bureau can do) seems perfectly
sufficient. I can only see the dots with a loupe, and the print comes
out nice and smooth.
I also found out that Dan's "platinum correction curve is not appropriate
for *my* paper, so I am working on that now. When I get something good I
will make it available to anyone who would like it.
David