Scanners

A scanner allows you to convert photographs, slides, and documents into digital files that you can add to web pages, send as email attachments, and include in presentations.

There are several different types of scanners; they range from the high-end drum scanners used by professional printers to very inexpensive hand-held models. There are also slide scanners, which are designed specifically for use with photographic slides. The most versatile and common type of scanner, however, is the flatbed scanner.

Flatbed Scanners

Not all flatbed scanners are the same. There are two main specifications that you should consider when evaluating one of these devices ---- color depth and resolution. Color depth indicates how many colors the scanner can capture, measured by how many bits are assigned to each pixel. Basically, the minimum color depth for scanners is 24 bits and the more bits a scanner has, the more subtle gradations of color are available. Also the better color depth, the more "accurate" the color is.

Resolution is measured in dots per inch, often abbreviated "dpi". Again, as in digital cameras, dpi is designated with expressions such as 600 x 1200 or 1200 x 2400 ---- pixels per inch horizontally and pixels per inch vertically. The more pixels you have, the higher resolution the scanner.

Don't be confused between optical resolution and interpolated resolution. The former is the actual capability of the hardware, but the latter is a software enhancement that can improve the resolution in certain types of photographs, but usually at the risk of softening the image. It is best to ignore interpolated resolution when evaluating scanner performance.

Using the Scanner

Flatbed scanners usually connect to the USB port of your computer (although some models use the parallel port) and come with software that permits some control of the scanning process. While automatic scanning settings may work ok, you may also get better results if you take some time to consider the options you should use for those settings that you can control manually. These may include such things as specifying the type of media you are trying to scan (color photograph, black & white photograph, document), the color depth, and the resolution. For instance, if you want to digitize a black and white printed document you shouldn't use all the same settings as for digitizing a color photograph.

When scanning a color photograph, you probably should scan and store the image with the highest color depth possible (to try to assure the best reproduction of the colors present in the photo). But you may not always want to scan the image in the highest possible resolution. For example, if you're converting a large color photograph to a small image for a web page you don't need high resolution for a computer screen.

Higher resolution translates into larger file size, which means longer download time for images on the web. In addition, since monitors have specific resolutions, if they try to display images with very high resolutions, the images will appear very large: very wide and/or very tall. Some high resolution images may, therefore, display much larger than the monitor screen size, requiring scrolling in either or both of the horizontal and vertical directions. Generally, users will likely find the need for such scrolling to be an annoyance.