Document Management Software

Scanner Basics

Choosing a scanner entails balancing the quality of the output, speed, driver, and software bundle. Fortunately, even moderately priced scanners are acquiring advanced features like 2400-dpi resolution, transparency adapters, and USB 2.0 connections.

Today's consumer scanners commonly have optical resolutions of 2400 dots per inch, and that's likely to remain the maximum you'll see for a while. Most home and business scanners tend to be inexpensive and have a fairly low profit margin, so instead of upgrading the core hardware, manufacturers are making scanners easier to use.

HP, for example, will add a 4-by-6-inch photo feeder to an upcoming model so you can scan snapshots faster; Epson is incorporating its Print Image Matching technology into newer units, which will simplify color calibration between the scanner, your system, and Epson printers. Support for Vista and Windows XP is now nearly universal among new models, and we have encountered no compatibility problems in our testing.

• Scanner type: Most scanners on the market today are flatbed scanners, so named because the scanning surface is flat. With a flatbed scanner, you place the object you want scanned onto a slab of glass beneath a cover (much like a copying machine). In addition to flatbed scanners, you'll also see sheet-fed scanners, handheld scanners, photo scanners, and multifunction peripherals that incorporate a printer, scanner, and fax machine into one device. Sheet-fed scanners were once prevalent, but they have decreased in popularity because they're less versatile than flatbed scanners: They work best for individual text pages. Because you feed the document you want scanned through a feeder, much like a fax machine, photographs can emerge bent out of shape--and you can't cram a book through a feeder.
• Optical resolution: For displaying photos on the Web or printing 3-by-5 or 4-by-6 snapshots, 100 dots per inch is plenty of resolution; for capturing text using optical character recognition, 300 dpi is standard; and any scanner on the market can easily perform those tasks. But if you want to make 8-by-10-inch or larger photo prints, or to enlarge smaller images, opt for a scanner with 1200 dpi or 2400 dpi of optical resolution. You'll have more flexibility in editing your image if you start with the highest possible resolution. Be warned, however, that high-resolution images take up a lot of hard disk space--for example, a 1200-dpi, 4-by-6-inch photo can consume 25MB. In addition, scanning at high resolutions tends to take longer.
• Color depth: The amount of color (and gray-scale) data a scanner can recognize and save, termed color depth, is measured in bits per pixel. Since a scanner can usually capture more data than its driver can save, you'll frequently see a qualifier appended to the bit-depth spec, such as 48-bit internal or hardware color, which describes how much data the scanner can recognize. External or true color describes how much data the scanner's driver can save. For almost all types of general-purpose use, 24-bit external color depth is sufficient.
• Sensor technology: Flatbed scanners have one of two types of sensor technology: a charge-coupled device (CCD) or a contact image sensor (CIS). CCDs, the older technology, might sound familiar as they're also used in digital cameras. CIS sensors are a recent innovation in scanners. Although they produce slightly lower-quality scanned images, CIS-based scanners can be much smaller and use far less power than CCD-based scanners. (CIS-based scanners can be powered through a USB cable.)
• Automatic document feeder (ADF): For handling high-volume optical character recognition or for scanning pages that are longer than a flatbed's scanning surface, an automatic document feeder can be helpful. ADFs are typically built into or replace the scanner's lid. HP and Microtek offer aftermarket ADFs for some of their models, but the total cost (around $200) is higher than if you choose a scanner that includes an ADF at the outset.
• Interface: Synchronizing their release schedules to conform to the expected integration of USB 2.0 onto computer motherboards, scanner makers are delivering products with USB 2.0 interfaces (which are backward-compatible with USB 1.1 connections) to market. We haven't seen great speed jumps from USB 2.0 scanners so far. Scanners with FireWire connections (which typically cost more and are designed for professional users) are noticeably faster than lower-cost units equipped with either USB interface.

More Information

• Scanner resource center
• What to consider when buying a scanner?
• The difference among entry level, mid-range, and high-end scanners.
• Scanner shopping tips
• Scanner basics
• Scanner terminology
• Scanning tips
• What is TWAIN?