Editing Image scanner (section)

=== Drum ===
{{Main|Drum scanner}}
[[File:1977 Januar Wuppertal 027.jpg|thumb|A [[drum scanner]] ([[Linotype-Hell|Hell]] Chromagraph DC 300) being operated]]
A [[drum scanner]] is a type of scanner that uses a clear, motor-driven rotating cylinder (drum) onto which a print, a film negative, a transparency, or any other flat object is taped or otherwise secured. A beam of light either projects past, or reflects off, the material to be scanned onto a series of mirrors, which focus the beam onto the drum scanner's photomultiplier tube (PMT). After one revolution, the beam of light moves down a single step. When scanning transparent media, such as negatives, a light beam is directed from within the cylinder onto the media; when scanning opaque items, a light beam from above is reflected off the surface of the media. When only one PMT is present, three passes of the image are required for a full-color RGB scan. When three PMTs are present, only a single pass is required.<ref name=drumdef>{{cite web | date=n.d. | url=https://www.pcmag.com/encyclopedia/term/drum-scanner | title=Definition of drum scanner | work=PC Magazine | publisher=Ziff-Davis | archiveurl=https://web.archive.org/web/20230930230924/https://www.pcmag.com/encyclopedia/term/drum-scanner | archivedate=September 30, 2023}}</ref>

The photomultiplier tubes of drum scanners offer superior dynamic range to that of CCD sensors. For this reason, drum scanners can extract more detail from very dark shadow areas of a transparency than flatbed scanners using CCD sensors. The smaller dynamic range of the CCD sensors (versus photomultiplier tubes) can lead to loss of shadow detail, especially when scanning very dense transparency film.<ref>{{cite web | url=http://www.dl-c.com/Temp/downloads/Whitepapers/Scan.pdf | title=Scanners and How to Use Them | last=Sachs | first=J. | publisher=Digital Light & Color | date=February 1, 2001 | access-date=November 8, 2015}}</ref> Drum scanners are also able to resolve true detail in excess of 10000 dpi, producing higher-resolution scans than any CCD scanner.<ref name=drumdef />