By Adam Crawford
1) Scanning film is better than scanning prints.** Scanning a negative instead of a print can give you more resolution and better dynamic range. A 35mm negative has more color information in its different layers (red, blue, and green) than a print can reproduce. No matter how large the print, the negative will always give you the best possible scan, because it contains more contrast, luminance, and color information.
2) It's not the type of scanner that counts—it's the type of sensor**. You used to hear advice to use a dedicated film scanner rather than a flatbed. But now it's more a matter of preference, as flatbeds' resolution has nearly caught up to film scanners. Instead, pay attention to the sensor they use, especially in low-cost scanners. CCD sensors generally provide better tonal and color reproductions with less noise than Contact Image Sensors (CIS) do, even if the resolution is quoted as the same.
3) Resolution can be misleading when scanning a print.** 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 high quality, 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.