While scanners can be very expensive, there are a number of features that you may want to consider before you pick one off the shelf.
What resolution should you get?
The resolution of a scanner refers to the maximum number of dots per inch (dpi) a scanner can capture. Resolution can range from 600x600dpi, which is fine for most day-to-day uses, to 1200x2400dpi, which is better if you plan to do sophisticated photo editing. Be careful of the term "interpolated resolution" which refers to a method of filling in the spaces between pixels, but has little to do with the actual resolution.
What do they mean by 24 bits?
"Bits" refers to the number of digital bits captured per pixel -- in other words, the number of colors that can be processed. This is known as color depth. Be aware that while the internal color depth may be stated as being 48 bits, many graphics applications can only handle up to 24 bits.
What kind of documents can I scan?
This can be very important when you're considering a scanner. Some low-cost scanners can only handle standard 8.5 x 11-inch paper, which could be limiting if you need to scan a legal-sized (8.5 x 14-inch) document. You also probably want to look at whether you can remove, or lift up, the cover, in order to make room for books and other bulky documents.
Can I scan transparencies or film?
If you're going to want to scan slides or negatives, you should purchase a scanner that has an adapter available. However, if you plan to regularly scan large numbers of negatives, look for a specialized film scanner -- it may be more expensive, but it will do a better job on your film.
