The drum scanner gets its name from the clear acrylic cylinder, the drum, on which the original artwork is mounted for scanning. Depending on size, it is possible to mount originals up to 20"x28", but maximum size varies by manufacturer. "One of the unique features of drum scanners is the ability to control sample area and aperture size independently. The sample size is the area that the scanner encoder reads to create an individual pixel. The aperture is the actual opening that allows light into the optical bench of the scanner. The ability to control aperture and sample size separately is particularly useful for smoothing film grain when scanning black-and-white and color negative originals.
While drum scanners are capable of scanning both reflective and transmissive artwork, a good-quality flatbed scanner can produce good scans from reflective artwork. As a result, drum scanners are rarely used to scan prints now that high-quality, inexpensive flatbed scanners are readily available. Film, however, is where drum scanners continue to be the tool of choice for high-end applications. Because film can be wet-mounted to the scanner drum, which enhances sharpness and masks dust and scratches, and because of the exceptional sensitivity of the PMTs, drum scanners are capable of capturing very subtle details in film originals.