I want to create an archive on my computer of some colour photos (prints) that I have. What would be the best dpi resolution to set my scanner to? I'm thinking that I may want to print off photos on photographic paper from the files at a future date so I think I need a reasonably high resolution. I can't see the need to email the files in the future.
I always scan at 600dpi to allow for losses in the scanning process. Tuvok is absolutely right though, professional eg magazine printing is done at 300dpi.
When I was a lad I worked with high-quality camera lenses, measuring their resolution capabilities. If you scan a target at 300 dpi with a lens capable of resolving 600dpi the overall resolution is 1/(1/300 + 1/600) ie 200dpi.
Scanning is quite a slow process, particularly the higher the resolution you go for. I'd go for the highest resolution you have the patience to wait for - you don't want to have to do it all again.
I had some done professionally and they came back at 600dpi. But in the days when I had photos published in good-quality colour magazines 300 seemed to be fine. It probably depends how big and how perfect you want them and how much time you have.
300dpi for printing, but if you want to send them as email attachments you could resize them with image resizer. 'save as' the smaller version so you keep them both for future use.
I agree with bhg481. While you are scanning in, do it at the highest res you can. You can always use the hi res originals to make lower res copies, but you can't increase the "true resolution" of a scan, ie make it so you can see more detail, you can only add more pixels per inch.