Scanners

Scanners have become a popular addition to the home computer system due to the affordability of some of the lower-end scanners. Scanners employ various technologies to transfer your physical documents or pictures to digital format which can then be printed, displayed to your monitor or sent to others electronically; you should be passingly familiar with the technology used before buying.

Technology

CIS (Contact Image Sensor) technology used to be the standard for flatbed scanners, but has become less desirable in favor of CCD (Charge Coupled Device) since the latter results in a lighter, smaller and more affordable scanner. A CCD scanner accepts light and converts it to electrical charges which is stored and converted to digital data by the software.

Types of Scanners

The type of scanner you choose will depend on your needs. This article is aimed at flatbed scanners as they are by far the most popular type of scanner for the average home computer user. A flatbed scanner consists of a glass plate, underneath which the CCD array moves to detect light from whatever is laid on top of the glass. The main problems with flatbed scanners are that they take up quite a lot of desktop space, and you must lift the lid and replace your document whenever you want to scan something new. If you plan on using your scanner to scan a large number of documents, you might consider a sheetfed scanner with an automatic document feeder. The CCD array in a sheetfed scanner is stationary; the sheets themselves move instead. The last type of scanner is the handheld scanner which you should only consider if you must have a portable scanner. They are a bit of a pain since you generally have to scan things several times to get an acceptable reproduction.

Bit Depth

As with most other sophisticated technology there are a few numbers associated with scanners that you will want to understand. The first is bit depth, which refers to the number of bits the scanner can remember for each pixel of an image and profoundly affects the overall quality of the scan, especially when scanning color photos. The higher the bit depth, the better the scanner will be at distinguishing different shades of color. You probably want a bit depth of at least 24, which will theoretically allow your scanner to represent about 16 million colors.

Resolution

Of course, a high bit depth won't help you at all if the scanner resolution is too low. The resolution of the scanner determines the size of the scanning area that will be represented by each pixel. Scanners will often specify two different resolutions: Optical and interpolated. The optical resolution is the one you are interested in as it refers to the true resolution; interpolated resolution results from 'averaging' information from true pixels to generate extra pixels. Optical resolution is measured in dots per inch (dpi) and obviously the higher the resolution the better. Most users will be satisfied with a resolution of 300 dpi, but if you plan on scanning very small images such as slides or photo negatives, you will probably want 600 dpi or even higher.

Speed

A scanner's speed can be important; many people overlook this quality in a scanner and consequently some scanners crawl along, taking forever to scan a single image. You should expect a flatbed 600 dpi scanner to take about a minute and a half for a single scan. A 300 dpi scanner should take about half that time.

Modern scanners are affordable and easy to use and therefore make a useful addition to any computer system.