Editing Compositing (section)

==Multiple exposure==
[[File:Keaton Playhouse 1921.jpg|thumb|right|''The Playhouse'' composited using [[multiple exposure]]s to show nine copies of Buster Keaton on screen at once.]]
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An in-camera [[multiple exposure]] is made by recording on only one part of each [[film frame]], rewinding the film to exactly the same start point, exposing a second part, and repeating the process as needed. The resulting negative is a composite of all the individual exposures. (By contrast, a "double exposure" records multiple images on the entire frame area, so that all are partially visible through one another.) Exposing one section at a time is made possible by enclosing the [[photographic lens|camera lens]] (or the whole camera) in a light-tight box fitted with maskable openings, each one corresponding to one of the action areas. Only one opening is revealed per exposure, to record just the action positioned in front of it.

Multiple exposure is difficult because the action in each recording must match that of the others; thus, multiple-exposure composites typically contain only two or three elements. However, as early as 1900 [[Georges Méliès]] used seven-fold exposure in ''L'homme-orchestre/The One-man Band''; and in the 1921 film ''[[The Playhouse (film)|The Playhouse]]'', [[Buster Keaton]] used multiple exposures to appear simultaneously as nine different actors on a stage, perfectly synchronizing all nine performances.