Typical resolutions range from 600 to 1200 dpi . In addition to recent increases in resolution and bit depth, further quality improvements in flatbed scanners have been achieved by arranging the optical system within to reflect the image back to a stationary CCD array rather that risk vibration through moving the CCD along the image. This also leads to a more compact system as evidenced in the 'slimline' models which are now available. Film scanners are typically used for digitising photographic negatives and transparencies. Current typical resolutions are around 2700 dpi with some models offering 4000 dpi .
Drum scanners are mainly the province of scanning bureaux and high quality professional work.
The drum can be loaded with several items at once and the driving software can separate the images from another. They really need a dedicated workstation to handle the data rate and file sizes generated. Network scanners are not unlike a network printer except that instead of sending a file from a networked computer and getting a paper copy out, you feed the scanner paper copy and get files back on the computer. Be aware that sending lots of full colour, high resolution A4 pages may seriously affect network performance. Miscellaneous and specialist devices, defying categorisation, will always be around.