Few digital libraries offer high quality scans that allow paper structure and ink layer thickness analysis.

But, is it worth to use them create a few GB PDF/DjVu if books are mainly intended for reading and not for scintific reserch on printing technology?

We should not reject any usable resolution.

Ankry

W dniu 2017-05-22 21:03:37 użytkownik Yann Forget <yannfo@gmail.com> napisał:

As others say, 2 Mpixels should be the minimum resolution, although it is a bit small to do any work (i.e. restoration).

That's the minimum requirement for quality and featured images on Commons.

For doing restoration, it is quite comfortable around 12 Mpixels (4000 x 3000).

That's what most cameras offer today.