Microfiche scanning

Pete Turnbull pete at dunnington.u-net.com
Thu Apr 21 11:42:22 CDT 2005


On Apr 21 2005, 10:43, Jim Leonard wrote:

 So what *is* enough?  The last microfiche I read at my local library
was 12
> pages by 16 pages on a 4"x6" film, so we have roughly (12/4)*(16/6)=8
pages per
> inch of film.  150 DPI is the absolute bare minimum for a readable
page, so a
> scanner would need a minimum resolution of (150*8)=1200 DPI just to
get
> something discernable.

Um, your maths is off.  Assuming 150 dpi is the minimum acceptable for
well-printed text (and some DEC fiche is anything but), and a page is
8" wide, you need 1200 dots per page width.  A page width on the fiche
you describe is 6/16 inches, so you need 16/6 * 1200 dots per inch,
which is 3192 dpi.

Another way to look at it is if an 8"-wide page is 6/16" or 3/8" on the
fiche, it's .04687 of original size, or about 21 times reduced.  So 150
dpi becomes 3200 dpi.  The equivalent resolution to get 600 dpi on the
original page would be 12800 dpi.

-- 
Pete						Peter Turnbull
						Network Manager
						University of York



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