1. Computing

Scanner Resolution and Color Depth


For scanners, resolution refers to the amount of information, calculated in dots per inch, that the scanner can read. More dots equals higher the resolution, and thus better-looking scans (low-resolution scans sometimes have big and obvious squares of pixels).

Keep in mind, however, that high-resolution scans are liable to have mighty big file sizes, meaning they’ll take up a lot of room on your hard drive, and could take a while to open, edit, and print.

How Much Resolution Do You Need?

How high a resolution you need depend on how you’re planning to use the image.

  • Web posting: Most computer monitors can display 72 dpi maximum (a little higher for high-definition monitors), so if you’re scanning something that will be seen on the Web or will go in an e-mail, scan at 72 dpi. You won’t lose anything if you scan at a higher resolution, but you won’t gain anything either (except in terms of file size, which could mean a lot to those on the other end of the e-mail).

  • Photos: Unless you’re planning on enlarging photos, you’ll get great picture quality by scanning at 300 dpi. If you’re going to double the size of the original, double the dpi.

  • Image editing: Follow the “double the dpi” rule if you’re planning on cutting the original down by cropping it.

Color / Bit Depth

Color or bit depth is the amount of information the scanner gets about the thing you’re scanning; the higher the bit depth, the more colors get used and the better looking your scan will be. Grayscale images are 8-bit images, with 256 levels of gray. Color images scanned with a 24-bit scanner will have nearly 17 million colors; 36-bit scanners will give you more than 68 billion colors.

Again, the trade-off is toward huge file sizes. Unless you’re a professional photographer or a graphic designer, there’s not much need to worry about bit depth, since most scanners have at least 24-bit color depth.

Related Video
Create a Color Sketch From a Photo in Photoshop Elements
Convert Color Photos to Black and White in Photoshop

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