And unless the user is willing to place each page on the scanner individually, they require an automatic document feeder to handle large numbers of documents. Over the last few years, personal sheetfed scanners have grown in popularity. These units are more like a fax machine than a copier, because they move the page being scanned past the scanning head, rather than the other way around. Sheetfed scanners also tend to be less exact than their flatbed counterparts, because of the difficulty of moving a sheet of paper without introducing distortions. Still, a sheetfed scanner is a good choice for handling paperwork without giving up much desk space.
Some items demand special handling during scanning.
Slides, for instance, require a scanner that passes light through the image rather than reflecting off light off it. To meet these requirements, several manufacturers have developed dedicated scanners that handle only 35mm slides. These devices are usually much more expensive than flatbed or sheetfed scanners, and are much less versatile, but they are still the right choice for those who need to make high-quality scans of more than a few slides. Before the advent of desktop scanning, most images were loaded into computers through drum scanners. Expensive and difficult to operate, these units were found primarily in color prepress companies.