Guides (Scanning)

Scanning - Image quality

Color balance, the ability to capture neutral colors in neutral form. If you scan a black-and-white photo in color and the result has a color tinge, you can bet that the colors will be off on your color photos, too.

Color accuracy, or the ability to capture colors that closely match the original.

Calibration for screen or printer to give tonal quality and color accuracy. Images that look good on screen will not necessarily look good at the printer, and vice versa. You'll want to calibrate for both screen and printer; make sure you use the appropriate calibration file when you scan, typically by telling the Twain driver the final destination for the image.

Noise level and the closely related signal-to-noise ratio are important indicators of how much detail you'll be able to see in a scan. Turning down the brightness settings also reduces the amount of noise in an image.

Color registration—a measure of how well the three colors line up with each other—isn't usually an issue for color photos but may be an issue if you're scanning line art. If the registration is off, you will see an extra "halo" of color at the edges. When you're printing to an ink jet or laser printer or scanning to a Web page, even a full pixel off is generally acceptable in a 600-dpi scan, though it will be noticeable to those who look for it in 300-dpi scan.

Image quality can be a subjective matter. The default settings of the HP scanners, for instance, tended to boost and oversaturate colors to impart a warmer tone to photos. This could be a desirable effect for many users, even if it's not precisely true to the original.

(Stone, M.D.,1997), Ziff-Davis Inc. on WWWeb.