An optical printer is a device consisting of one or more film projectors mechanically linked to a movie camera. It allows filmmakers to re-photograph one or more strips of film. The optical printer is used for making special effects for motion pictures, or for copying and restoring old film material. Common optical effects include fade outs and fade ins, dissolves, slow motion, fast motion, and matte work. More complicated work can involve dozens of elements, all combined into a single scene.
In the late 1980s, digital compositing began to supplant optical effects. By the mid-nineties, computer graphics have evolved to rival and surpass what was possible with optical printers, and optical printing has all but gone. Improvements in film scanners and recorders allow for a complete feature film to be ingested into computers, have any effects applied to it, and output back to film.
Today, optical printing is mostly used as an artistic tool by experimental filmmakers, or for education purposes. As a technique, it proves particularly useful for making copies of hand painted or physically manipulated film.