Fiche scanning (was Re: [Simh] Listings of XXDP test and maindec'sfor 11/70)

Paul Koning Paul_Koning at
Wed Apr 15 08:59:24 CDT 2009

> Jan-Benedict Glaw wrote:
> > On Tue, 2009-04-14 10:52:00 -0500, Jules Richardson
> <jules.richardson99 at> wrote:
> >> The DEC ones I've seen are extremely high resolution - from memory,
> >> something like 11 x 13 A4 pages on a fiche around 1" x 1.5".
> >
> > If this is right, then there's a scale factor of about 1:90 to 1:100
> > involved.  That should tell everybody why even a good consumer-grade
> > scanner will not do the job. To get the equivalent of a 300dpi scan,
> > you'd need to have about 30000dpi. Nothing any el-cheapo scanner
> could
> > handle. (Let alone the problem of getting the sheet properly into the
> > light's focus.)
> you are confusing linear pixel density with areal pixel density.
> the 11"x13" fitting in 1"x1.5" implies a 11:1 scaling in density, so
> 300
> dpi would be 3300 dpi.  still very high for typical consumer grade
> scanners.  I believe 2400 dpi actual (not interpolated) is available on
> decent models, though.

I think the confusion is in: 'on a fiche around 1" x 1.5"'

J-B read that as the size of the whole fiche (with lots of A4 images on it).  I think you actually meant that each page image is that size.

The truth is most likely in between: page images (on DEC fiche at least) are a bit smaller than that, and also they are usually images of line printer size pages (A3, not A4).  So a 2400 dpi scanner is about a factor 3x too low for acceptable quality.  (And yes, that ignores other issues like ability to hold the fiche flat enough and focus well enough.)


More information about the cctalk mailing list