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Tutorial: Scanner Types -- Flatbed Scanners, Film Scanners, Drum Scanners
There are three major types of scanners in common use today: flatbed, film and drum. They have differing uses, strengths and weaknesses. You will see these terms as you shop for scanners or scanning services. This article should help you make sense of these terms.
The most common scanners are flatbed scanners. These are a type of reflective scanner that commonly sits flat on a desk. Flatbed scanners are adapt at scanning pieces of paper, objects, photo prints, and other opaque items. Using a flatbed scanner is relatively simple. First you open the cover and set your subject on the glass surface, and close the cover. Usually you can then run the scanner software, tell the scanner what resolution to use for the scan and possibly set a few other simple preferences. The scanner will then begin scanning your subject. After the scan is complete, you can remove the subject from the surface. Some scanning software comes with simple editing tools, or you can edit your image by yourself.
Reflective flatbed scanners can not scan transparent objects such as slide or negatives, however, unless they are equipped with a transparency adapter. A transparency adapter allows the scanner to shine light through the film. Please see our description of the differences between reflective and transmissive scanners for more details. With a transparency adapter, a flatbed can scan slides and negatives. Generally speaking, the quality of such scans is not as good as those from dedicated film scanners or drum scanners. Some higher end flatbed scanners do a very passable job on films, however. For example, Epson has a number of higher end units such as the V750 that do a fine job on films, particularly when used with fluid mounting techniques (see below).
Flatbed scanners can be very inexpensive, even with a transparency adapter. Flatbed scanners with good film scanning capabilities are more expensive, however.
Film scanners are specialized transmissive scanners made to scan film strips and mounted slides (negatives and positives). Film scanners have optics and electronics specifically catered to scanning film. Because of this specialization, film scanners achieve better results when scanning film than flatbed scanners. Some film scanners include feeder attachments that can make doing many scans easier and faster. Having an automatic feeder is very helpful for more extensive scanning work, such as a large slide collection. Only a few models of film scanners have this capability, and it is generally a fairly expensive optional attachment. Film scanners are relatively easy to operate.
Some scanners, such as the Nikon 5000 ED, are able to scan only smaller format films, such as 35mm and APS. Other types of scanners are used for larger film formats, such as 120 medium format films (in addition to 35mm and other smaller formats). An example of such a medium format film scanner is the Nikon 9000 ED. Overall, film scanners are less flexible than flatbed scanners, which are able to scan a wider variety of film formats.
Film scanners are moderately priced, from $400-$1500 (with a few high end models going up to perhaps $20,000).
The last type of scanner that we discuss here is the drum scanner. Drum scanners work differently than the other two types of scanners. Flatbed and film scanners rely on light from a source hitting a microchip called a CCD (Charged-Coupled Device). The drum scanner, instead of a CCD, has a photo multiplier tube which is a type of vacuum tube that is highly sensitive to light. A beam of light, which can be focused quite small, is then moved across the image and the photo multiplier tube picks up the reflection. Drum scanners can generally scan any type of film.
Drum scanners are large, very expensive (up to $100,000), and very difficult to use. However, due to the extremely sensitive photo multiplier tube, you can obtain images that are higher quality than images from a CCD scanner. Therefore, applications requiring extremely high quality utilize a drum scanner.
Film is mounted in the drum scanner using a special kind of oil, instead of simply inserted into the scanner. This use of fluid mounting reduces the effect of dust and scratches in the film and reduces the effect of the film grain structure. Fluid mounting can be used in some flatbed and film scanners, though this is rather uncommon because of the expense, effort and mess involved.
The table below summarizes a few of the key differences between flatbed, film and drum scanners.