There are basically four different types of scanners: film, hand-held, flatbed, and drum.

• Film Scanners / Slide Scanners: Film scanners are small desktop scanners used to scan 35mm film and slides. Some of film/slide scanners include an APS (Advanced Photo System) film adapter for use with the APS film format.
  
  Slides usually are higher quality than prints and produce a higher quality scan. Slides are brighter than prints and have a higher dynamic range. Many slide scanners have resolutions in the 5,000-6,000 ppi range and can be very expensive to purchase.
  
  

• Hand-held scanners: Hand-held scanners are small instruments that you slide across the image by hand. They can only scan 2"-5" at a time so are only useful for small photos. They are sometimes called half-page scanners and are the least expensive type of scanners.
  
  

• Flatbed scanners: Also called desktop scanners, flatbed scanners range from inexpensive low-end scanners for hobby use to very high quality, expensive units used by professionals. They generally are not as high quality as the drum scanners.
  
  Images are placed on a glass bed either with or without a holder. The scan area varies in size from 8-1/2" x 11" to 13" x 18". Either the bed is stationary and the scanning head moves or if the bed moves, the scanning head is stationary. They are either a single-pass or three-pass scanner. Single-pass captures all the RGB colors by moving the light source over the image once. Three-pass scanners use three passes, one pass each for red, green and blue. The single-pass scanners are faster but the three-pass scanners are generally more accurate.
  
  Flatbed scanners can scan originals of varying thicknesses, and some are capable of scanning three-dimensional objects. You can add adapters for automatic page feeders. There are also templates you can use to hold pieces such as transparencies or slides.
  
  In traditional flatbed scanners, the scanning head moves in one direction only. There is a new technology called XY scanning which positions its scanning head along an XY axis. The scanner head slides both horizontally and vertically beneath the bed. The XY scanning technology assures high resolution and uniform sharpness of the entire scanning area. It also makes it possible to enlarge an image to a much higher percentage than the traditional flatbed.
  
  The highest resolution you can achieve without interpolation is about 5,000 dpi. With interpolation, the resolution may increase to about 11,000 dpi.
  
  

• Drum scanners: Also known as a rotary scanner, the drum scanner scans images that are mounted on a rotating drum. The drum spins rapidly in front of a stationary reading head on either a horizontal or vertical unit. The vertical ones are beneficial since they save on space.
  
  Drum scanners are generally higher quality but are also very expensive. Some have the capabilities to scan at a resolution of 12,000 dpi without interpolation. Drum scanners cost from $25,000 to several hundred thousand dollars and require trained operators to achieve the best results.
  
  Generally, drum scanners have a larger scanning area than the other types. Some offer scanning drums that are 20" x 24" or larger. The larger scanning area makes it possible to scan large items or a combination of several smaller items.
  
  The disadvantage of drum scanners is that the original image must be thin and flexible enough to be wrapped around the drum.

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