Flatbed scanners : a buyer's guide
Flatbed scanners are the most commonly used type of scanner because they have the best combination of quality and flexibility. Capable of handling everything from photographs to text documents, they are a brilliant all-rounder and perfect for general use. Prices have been slowly but steadily decreasing over the years and flatbed scanners are now reasonably affordable for the average consumer.
If you are looking to buy a flatbed scanner then there are a few technical terms you should become familiar with. The following is a brief guide to the most important technical features to look for in a scanner:
Bit Depth and Dynamic Range : the color edge
Bit depth is basically a scanner's ability to store a range of colors and the higher the bit depth the more colors the scanner can store. Most flatbed scanners range from 24 to 36 bits.
Dynamic range (or optical density) is an important feature to look at if you need a good graphics scanner because it measures the scanner's ability to pick up on varying tonal ranges. The measurement ranges from zero (white) to four (black) and most flatbed scanners have a range of 2.8 to 3.0. This is a good range for scanning photos as the higher the optical density, the better the tonal variation.
There are two types of resolution - optical and interpolated. Optical resolution is the best one to look at because it is a more accurate measurement of the scanner's ability to produce sharp, clear images . This is because optical resolution is measured in pixels per inch (ppi) and is quoted vertically and horizontally. The more ppi a scanner can pick up the sharper the image. Flatbed scanners with a resolution of 300ppi should be fine for general use.
Speed depends on resolution so the higher the resolution the slower the scanner. So for color scanners with a 600ppi resolution a good speed to look for is 100 seconds per page. Speed can also vary depending on the interface used to connect a scanner to your computer or network. SCSI connections are generally quicker than USB.
Software and drivers
Software that comes 'bundled' with a scanner normally contains a driver program, optical recognition software and image-editing software. Most flatbed scanners come with fairly efficient driver software capable of coping with general applications but don't expect sophisticated optical recognition or image-editing software.
The Internet can be an invaluable tool for finding information on a wide range of flatbed scanners but if you don't know what you're looking for it can take hours to find what you need. Decide what you need from a scanner before you even start looking and then you can narrow your searches according to your specific criteria. Once you have narrowed your search reading reviews on those models is a good way to compare their performance. Also check them out in a store.