[Milsurplus] scanning old photos/books

[J Forster]

Some scanners (and digital photocopiers such as are available at Staples and
other places) have a 'de-screen' option which fuzzes the original half-tone
dots and then re-digitizes. This can largely eliminate the Moiré effect, but
requires some tinkering to get it to work right.

If I want an absolutely exact copy of the original, I scan at a resolution
high enough to put about 9  ( 3 x 3) scanner pixels on EACH half-tone dot.
That's about what happens at 400 dpi on typical half-tones done with a 133
line screen.

Best,
-John



Wammes Witkop wrote:

> [snip]  And even is this sort of
> picture is called half tone - implying grays - in actual fact it is a
> rendering of grays by using bigger and smaller black dots, as is usually
> the fact with printed pictures. My preferred route is to scan in pure
> black and white at a high resolution and then indeed print at that same
> resolution. Play around with the threshold in order to get the best
> representation of the picture, so the dots do not turn out smaller or -
> worse! - start running together. This way you preserve (most of) the
> screening of the picture. There will always be artifacts, for instance
> because the dot-pattern does not align perfectly with your scanner. But
> results can be quite good.