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[filmscanners] Re: Pixels and Prints




Roger Krueger writes:

>>>>>>>>>>
Comparing digicam pixels to scanner pixels is misleading because scanner
pixels are
second-generation--4000 scanner pixels=2700 digicam pixels seems empirically
like a good
approximation, but I don't have research to prove this.
<<<<<<<<<<<

My estimate is 4000 scanner pixels=2400 digicam pixels. Here's a scan (the
left is an in focus scan and the right an out of focus scan of the same
area) first straight, and then carefully downsampled to 2400 dpi. (Velvia
100F)

http://www.pbase.com/image/22348855/original
http://www.pbase.com/image/22348935/original

>>>>>>>>>>
And comparing lines resolved between digicams and film is a little
misleading
anyway--digicam generally have pretty decent MTF right down to their
theoretical limit,
then fall off to zero. On film, the MTF starts to fall off sooner, but keeps
going longer.
Assuming 3 pixels/line pair, 300 dpi can resolve a hair under 4 lp/mm. 200
dpi is 2.6
lp/mm. Both well under the "standards" for a fine enlarger print of 6-8
lp/mm. The catch is
that at the 3 lp/mm frequency, the 300 dpi digital probably has better MTF
than the
enlarger print, even though it loses the ultimate resolution battle. The
reason you "need"
6-8 lp/mm from an enlarger print is not so much that you can actually see
that resolution
from a normal viewing distance, but that a 10% MTF at 6 lp/mm is a good
predictor of a 80%+
MTF at 2-3 lp/mm, which is what really matters.
<<<<<<<<<<<<

Agreed. This is, IMHO, exactly right.

David J. Littleboy
Tokyo, Japan

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