Digitization Guidelines
* work in progress
The German Science Foundation issued a set of guidelines for the digitisation of documents.[1]
In the following you find an excerpt from those guidelines that are especially relevant for institutes which digitise documents themselves.
Resolution and Image Quality
For scanning greyscale or coloured prints a minimum resolution of 300 dpi is suggested. Documents containing handwriting or maps with fine lines and small descriptions might require a scan resolution of up to 400 dpi. For generating bitonal scans, 600 dpi are requested.
Colour depth
Bitonal scans (b/w) are generated with a colour depth of 1 level (1 bit) per pixel. Greyscale images are digitised with 256 levels (8 bit = 1 byte) per pixel. Colour images use 3 colour channels (red, green, blue) with 1 byte per channel (= 24 bit = 3 byte per pixel), enabling 256 x 256 x 256 = 16.7 million colours per pixel. 24 bit provide a sufficiently high colour depth for colour scans. Scanning with 48 bit colour depth makes sense only in few cases where images need to be corrected or reworked after the scanning process.