What resolution should I scan a missing print set at?

Eric Smith spacewar at gmail.com
Wed Feb 18 19:41:45 CST 2015

On Wed, Feb 18, 2015 at 6:33 PM, Noel Chiappa <jnc at mercury.lcs.mit.edu> wrote:
> Hi all, I have a PDP-11 print set (MP00196, M9301 Bootstrap/Terminator) which
> is not online. I wish to scan my copy, and donate the scan to all the
> repositories.  What resolution should I scan it at?

If it's an original with decent reproduction quality and in B size
(11"x17"), then 300 dpi is adequate, provided that you scan it into a
lossless bilevel image format (e.g., TIFF Class F G3, G4, JBIG, or
JBIG2), which could be embedded into a PDF file.  Please do NOT use
anything that will apply lossy coding intended for continuous-tone
photographs (i.e., JPEG) to it, because that causes horrible artifacts
since JPEG deliberately throws away the high-frequency components and
blurs the edges of lines and text.

> I looked at a couple that are available as TIFFs, and they claim to be 600 dpi
> - that can't be right, is it?

With a lossless bilevel encoding, a 600 dpi scan will definitely be
bigger than 300 dpi, but not absurdly huge.

I'd recommend trying 300 dpi.  If you inspect the scanned images and
find everything easily legible (at least comparable to the paper,
which isn't always terribly legible), then there's no good reason to
go to 600 dpi.

If you're going to submit it to Al for Bitsavers, it's possible that
he might want it as a TIFF file, rather than already wrapped in PDF.
(I don't speak for Al, so I'm only guessing at his preferences, and in
actuality it would be best to check with him.)


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