The Specs Explained
As with any piece of high-tech equipment, a scanner's specifications can't tell the whole story. But you can use price, along with resolution, color depth, and other specs, to weed out the ones you don't want. With scanners in particular, higher prices indicate better components--so you really do get what you pay for.
When reading the resolution figures, note that the lower of the two numbers indicates how many dots the scanner can capture in each linear inch of the scan head (called the optical resolution). The larger number is the number of "lines" the head captures as the head scans each inch of the photo or document.
In general, ignore interpolated resolution, which uses software to add more information to an image. This attempt to sharpen images is generally not very useful.
On high-end scanners you may see a specification for dynamic range (or Dmax)--this indicates the sensitivity of the device in accurately rendering the lightest and darkest colors and shades in an image. Dmax readings of 3.2 or higher are considered good. It's worth noting that Dmax is a logarithmic system, so a scanner with a 3.6 or 4.2 rating has a significantly better dynamic range than a 3.2-Dmax-rated scanner.
Important: Resolution
The resolution indicates how detailed the digital image will be. The higher the numbers, the sharper the scans will tend to be. This is especially important when making enlargements; however, a higher resolution does not necessarily mean you'll get better color accuracy.
Somewhat Important: Scan Area
While few home users will need to scan legal-size documents, business users may find the letter-size scan area of most scanners too small. A larger scan area also makes it easier to scan large books, maps, drawings, paintings, newspapers, and tabloids.
Somewhat Important: Ports
Your PC must have a compatible port to connect with the scanner. Most scanners come with a USB 2.0 port, which is fast enough for small jobs. An older PC with only a USB 1.1 port will work with a USB 2.0-capable scanner, but the PC won't take advantage of the newer port's faster speeds. Scanners that have a FireWire connection are designed for professional users.
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