any of various methods of composing matter for printing, in which light images of type characters or graphics are projected in succession onto a photosensitive surface to produce a negative from which plates can be prepared
See photocomposition in American Heritage Dictionary 4
(fōˌtō-kŏmˌpə-zĭshˈən)
noun
The preparation of manuscript for printing by the projection of images of type characters on photographic film, which is then used to make printing plates. Also called phototypesetting.