Microfiche scanning

Paul Koning pkoning at equallogic.com
Thu Apr 21 08:58:42 CDT 2005


>>>>> "Jules" == Jules Richardson <julesrichardsonuk at yahoo.co.uk> writes:

 Jules> Am I right in thinking that a home flatbed scanner has
 Jules> absolutely no hope of providing the resolution needed to scan
 Jules> microfiche?

 Jules> We've got a *lot* of DEC documentation arrived on fiche (208
 Jules> pages per fiche, estimated 25000 sheets) and scanning some of
 Jules> the more useful bits would be nice. So far the cost from
 Jules> commercial companies has either been too high or the quality
 Jules> has been far too low to actually be useful :-(

I would think "it depends".   Some home scanners have optical
resolution of 4800 dpi or better.  That may be good enough.

Beware of inflated resolution figures.  A lot of scanners have very
high "resolution" claims but those are not real, they are fake pixels
made by interpolation.  Look for "optical" resolution, that's the real
number.  Also, in many cases there will be two numbers, e.g., 1200 x
4800; that means you have rectangular pixels, 1200 per inch in the
coarse direction.

You'd want a scanner where the smaller of the two optical resolution
figures is large enough.

How large is large enough?  For a paper scan, 200 dpi is about the
lowest you'd want, 300 is good.  So that makes 3300 pixels for an 11
inch high sheet.  So measure the page images on your fiche.  They are
probably the analog of 11 by 17 pages, so you'd want enough resolution
to give you about 3000 pixels across the height of a page image.

You'll also need a scanner with a "transparency" or "slide"
capability.  That means a back-light, typically built into the scanner
lid.  Those aren't all that common, though they are becoming more
common these days.

       paul




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