Scanner Resolution

Scanners - look for high optical resolution

Scanner resolution is specified in dots-per-inch (dpi) or pixels-per-inch (ppi). According to PC World, settings of 100 to 300 dpi produce good results when scanning photos, graphics or text for most home uses. When printing images, 300 dpi is an often-recommended resolution. However, if you plan on cropping, enlarging and editing photos, more resolution will help you do that without a loss in image quality. In general, if you want to scan and manipulate photos, slides and negatives, look for a scanner with a minimum dpi of 3200 -- beyond that level is likely more dpi than you'll need, but you'll be able to scan a small snapshot, edit the image and blow it up to an 8 x 10 without loss of detail.

Experts stress that a scanner's native optical resolution is more important than either "interpolated" or "enhanced" resolution, both of which are derived via software. Some scanners are advertised with two dpi measurements -- a lower measurement for the optical resolution and a higher number for the software-enhanced resolution. Reviews say you should disregard the higher interpolated resolution.

Dedicated slide and film scanners start at 4000-dpi resolution and go as high as 6400 dpi, but at that end of the scale, optics quality takes precedence over dpi specifications. Consumer Reports also recommends considering the scanner's maximum color-bit depth, which is important for what the experts call "dynamic range," defined as the ability to capture subtleties within light and dark gradations. Virtually all photo-oriented scanners tested now support 48-bit color scans, and some low-cost scanners, such as HP's Scanjet G4050 (*Est. $180), even support 96-bit color depth. That can be useful when scanning originals such as paintings or drawings, as those can have a color spectrum that exceeds what film -- or 48-bit scanners -- can accurately capture.

Nearly all scanners come with optical character recognition (OCR) software that transfers scanned text into an editable digital document. Editors note that getting good results with OCR can be tricky, especially when enlarging small images. If OCR is important, consider the quality of the scanner's bundled OCR software, or budget extra for a good stand-alone OCR application. Some scanners also include some image-editing software, such as Adobe Photoshop Elements, that will provide all the editing power most users need (although not as much as the full version of Adobe Photoshop).

Additionally, most scanners ship with some form of software that repairs flaws and removes dust spots from old or dirty originals. Often this feature is integrated into the scanner hardware itself. The most often-cited example is Kodak's Digital ICE Technology, in which the image is "cleaned" during the scanning process itself, not during later image editing. As you might expect, the capability and complexity of the software increases along with the sophistication and price of the scanner.