Choosing a flatbed, document or film scanner

There are three main types of scanners: flatbed, sheet-fed (semi-portable and fully portable models) and dedicated film and slide scanners. Flatbed scanners include a hinged lid, much like that of a copier. You place your original document or photo print on the plate, then close the lid and scan. Flatbed scanners can also include holders for scanning film or slides, making them extra flexible. You can also use them to scan bulky items like the pages of a book.

If your scanning needs involve documents rather than photos, film or slides, a sheet-fed document scanner is a good way to convert reams of paper documents to digital. Sheet-fed scanners that are not meant to be fully portable include an automatic document feeder (ADF), so you don't have to feed documents through the machine one at a time, and they look more like a fax machine or printer. Some sheet-fed scanners can be made portable by detaching them from a docking station or folding down a built-in document feeder, while strictly portable models are small enough to fit into a briefcase and may not include a document feeder at all.

A dedicated slide and film scanner can only scan slides and negatives.

Here's what the experts say to look for when buying a scanner for your home or small business:

  • Flatbed scanners are most versatile. These can scan documents, film, slides and three-dimensional objects.
  • Resolution matters most for photo scanning. Scanner resolution is measured in dots per inch (dpi) or pixels per inch (ppi). The Canon CanoScan 9000F, for example, has an optical resolution of 9,600 by 9,600 dpi, meaning it scans 9,600 dots per inch both horizontally and vertically. Most manufacturers reference just the first number; hence, the Canon is a 9,600 dpi scanner. Only the least expensive scanners offer fewer than 4,800 dpi; the Canon CanoScan LiDE 110 (*Est. $60) has a resolution of 2,400 dpi. Even these inexpensive scanners should be fine for most general-purpose document work or low-resolution photo scans destined for the Internet. Note that scanners intended solely for document work -- including high-end models -- usually have resolutions of 600 dpi, all that's needed for document scanning. 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.
  • Nearly all scanners are equipped with 48-bit color depth. Color depth refers to the number of colors that can be displayed, which is important for dynamic range, defined as the ability to capture subtleties within light and dark gradations. The higher the bit depth, the more colors used in the image; therefore, the larger the file size. For instance, 24-bit color corresponds to 16.7 million colors, and it's basic. If you'll be enlarging prints or scanning negatives or slides, opt for 48-bit because it can differentiate between subtle gradations. Some scanners, such as HP's Scanjet G4050 (*Est. $155), offer 96-bit color depth, and those can be a good choice if you scan original paintings or drawings, which have a wider spectrum of colors than photographs or slides.
  • Included software is standard. Scanners typically come with image-editing software, plus an optical character recognition (OCR) package that converts scanned text into an editable document. Photo scanners include software to edit and manage photos on your PC. Many also include a PDF converter. Even inexpensive models include some form of image correction software.
  • If you want to convert scanned text into an editable document, you need optical character recognition (OCR) software. 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 standalone OCR application.
  • For film scanning, consider buying a used model. If you have a limited number of film negatives or slides to scan, a used model may be a better value. Some manufacturers sell refurbished models. Be sure to look into return policies.

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