Within each type of scanner, individual models differ from each other in a number of ways. Though each manufacturer's product will have a different "look," what really counts is how a particular unit measures up on the following counts:

• Resolution
• Bit-depth
• Dynamic range
• Scanning method
• Scanning area
• Speed

These six criteria together determine why one scanner performs technically better than another, and we review each and suggest ways to measure each one. But there are other considerations to consider as well: the aesthetics of case design and the quality of construction, footprint (how much desk space is taken up), connection type (SCSI, parallel, USB, FireWire), bundled software and, of course, price.