Scanning question (Is destruction of old tech docs a moral crime?)

Paul Koning paulkoning at
Tue Jul 23 19:30:12 CDT 2019

> On Jul 21, 2019, at 12:16 PM, Jon Elson via cctalk <cctalk at> wrote:
> On 07/21/2019 05:16 AM, Joseph S. Barrera III via cctalk wrote:
>> What dpi qualifies as not "crappy"? 300dpi? 400? 600?
> Most of the text of these documents don't need super high resolution.  But, some contain hand-drawn schematics where an 11 x 17 original has been shrunk to 8.5 x 11" and hand-written signal labels and part types are VERY small.  These need to be scanned at high resolution, with several retries while adjusting the image threshold to make things readable.

Another example that might call for higher than normal resolution is oddball text, where subtle distinctions need to be visible.  An example of this can be found in the scans in the Knuth archive of the THE operating system sources.  Those are line printer listings printed with a typical medium-worn ribbon -- that's bad enough.  But the printer is upper case only printing mixed-case source material.  That was handled in that OS by overprinting upper case letters with periods.  In a clean original printout that's easy enough to see, but the scans seem to be about 300 dpi and with that the overprints are often not easy to see.  Since the source text is case sensitive this can be a problem...


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