Let me offer some direct help. Standards are great, but they are not very "direct" for answering basic questions such as your.
Humans can resolve 6 line-pairs per mm (lp/mm), the digital equivalent is 300 ppi. However, the Nyquist sampling theorem says that you need a minimum of twice the resolution of the analog material to capture it effectively. There is infinite detail in your documents, down to the paper fiber and surface texture. Humans, using their eyes, can not see more than 6 lp/mm of detail from the document, so setting your basic digital capture at twice the "analog detail" that humans can "see" is a good default. I can provide a very good tool to explain this, but it is long an complicated, just accept that one needs 600 ppi digital to capture 6 lp/mm (or 300 ppi) analog material such as document and photos. I would use color (as you are) so you can see age, ink and paper color as well as any stamps or other editing and identifying marks. The next point is 24 bit vs 48 bit color (8 bit vs 16 bit B&W). If you do not plan to manipulate the images to bring up fading ink or faint passages, then 24 bits will be fine. If you plan to do forensic type work with the images, consider 48 bit capture, and possibly more resolution such as 900 or 1200 ppi. All this will make fairly large files sizes. I recommend TIFF. However, the JPEG2000 format, used in lossless color mode (not in high compression lossy mode) will not harm image detail or color, and will save 50% to 75% in file size. More compression is possible but color will start to be effected. Only tests will show weather this is acceptable to your project. Read some standards and guidelines. I have a document on this subject if you want it, just ask. Tim Vitale Paper, Photographs & Electronic Media Conservator Film Migration (still) to Digital Format Digital Imaging & Artwork Facsimiles Preservation & Imaging Consulting Preservation Associates 1500 Park Avenue Suite 132 Emeryville, CA 94608 510-594-8277 510-594-8799 fax tjvitale at ix.netcom.com Albumen website (2001) http://albumen.stanford.edu/ VideoPreservation Website (2007) http://videopreservation.stanford.edu
