Selecting a Scanner

[Sunite]

Types of Scanners
Scanners come in a variety of configurations. The type you should consider depends on both your planned scanning needs and your budget.

Drum scanners. This type of scanner provides the highest level of image quality. They are typically found at professional printing businesses. In a drum scanner, the original is attached to a cylindrical drum and rotated past the sensing elements. These scanners are very expensive, with capabilities that go well beyond the needs of desktop scanning.
 
Flatbed scanners. This type of scanner provides a flat glass surface onto which the original is placed. The illumination and sensing elements move under the glass to scan the image. Flatbed scanners are available in a wide range of sizes, prices, and capabilities. Some flatbeds offer a transparency scanning adapter as an option.
Single sheet scanners. This type of scanner is designed for single sheets of paper. You insert one edge of the paper in a slot and the scanner grabs it, feeds it past the sensing array, and passes it out the other side. Some single sheet scanners are even integrated into keyboards. Such scanners were originally designed for digitizing documents and images for archiving, and many models are not suitable for creating high-quality images.
Sheet-fed scanners. These scanners take a stack of pages and scan them in sequence while you get coffee. Some even do duplex (2 sided) scans. They are very useful in some situations but not much use to the philatelist.
Photo scanners. This type of scanner is designed to scan snapshots up to approximately 4´6 inches in size. Some are separate desktop units; others install directly into a computer much like a diskette drive.
Hand scanners. This type of scanner requires the user to manually scan an image. Hand scanners look something like an overgrown mouse. To scan, you manually drag the unit over the original document. Handheld scanners are suitable only for small originals that are no wider than the scanner itself. In theory, most hand scanners permit you to scan a wide original in two or more passes and "stitch" the scans together into a final image. This, however, never works as well as the manufacturers claim.
Slide scanners. This type of scanner is designed for scanning slides (transparencies) rather than opaque originals, such as photographic prints. While rarely relevant for scanning philatelic material, a dedicated slide scanner is the best choice for scanning slides. Some flatbed scanners come with transparency adapters but they do not provide top quality results, particularly with small slides such as 35mm. Slide scanners have very high resolution, typically a minimum of 2400 dpi, required for getting all the details out of your slides. Many slide scanners also have the ability to scan color negatives and to convert the negative image to a positive image.
For philatelic purposes, a flatbed scanner is undoubtedly the most versatile. You can scan anything from a single stamp to an entire stock book or album page. A hand scanner may be a viable alternative, particularly if your budget is tight. Their width limitation does not matter so much for stamps and covers. I have also seen single sheet scanners and photo scanners used successfully for philatelic purposes, although they require that the item being scanned be sandwiched between clear plastic sheets for feeding into the scanner.