Tip of the Day: 5 Things You Didn’t Know about Scanning

By Adam Crawford
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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.
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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.
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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 4×6-inch photo into an 8×10, 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.

4) Think about the intended size of your final print before scanning a negative. Scanning at 2000 dpi, or close to this number, is sufficient when you’re using a flatbed/ film scanner, and leaves you with less grain for standard-sized prints. But to maintain the highest image quality, scan at the highest dpi you can. There are some simple numbers to remember for scanning different film sizes: For 35mm film, 1200 dpi gets you roughly a 4×6- inch print; 2400 dpi gets you roughly an 8×10; 4800 dpi gets you roughly a 13×19; and 6400 dpi gets you roughly a 16×20. If you want to make a billboard, use a drum scanner, which will give you the best resolution and a monster-sized file intended for large-scale reproduction.

5) More bit-depth means a bigger file. For basic scans of a print, there’s no need to go above a 24-bit (8 bits per color channel) scan. For film scanning, it depends on what you’re using the image for and what kind of workflow you prefer. Some photographers like  to do a scan that contains as much information as possible, at 48-bit (16 bits per color channel) with all scanner driver corrections turned off. But if you just want to make a film scan with little or no post-scan editing, stick with 24-bit and save some hard drive space.