How much resolution you need depends on how you'll use the scan. Any current flatbed scanner should provide enough resolution to do the job. A formula to figure out how much resolution you need: Take the short side of your original and divide that into the short side of your output size, then multiply that by 300 for the dots per inch at which to scan. So, to make a 4x6-inch photo into an 8x10, divide the 4 inches into the 8 inches for 2, times 300, yielding a 600-dpi print. Of course, if the original print isn't very highquality, or if it comes from an inkjet printer, blowing it up will make any imperfections (or ink droplets) more visible-another reason to start with a negative.