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.
The first, simple optical printers were constructed early in the 1920s. Linwood G. Dunn expanded the concept in the 1930s, and the development continued well into the 1980s, when the printers were controlled with minicomputers. Prime examples of optical printing work include the matte work in Star Wars (1977).
In the late 1980s, digital compositing began to supplant optical effects. By the mid-nineties, computer graphics had evolved to rival and surpass what was possible with optical printers, and optical printing is now all but gone. Improvements in film scanners and recorders allow for a complete feature film to be processed by computers, have special effects applied, and then be processed back to film.
Today, optical printing is mostly used as an artistic tool by experimental film makers, or for educational purposes. As a technique, it is particularly useful for making copies of hand painted or physically manipulated film.
As in any analog process, every optical "pass" degraded the picture, just like a photocopy of a photocopy (although the degradation can be greater with contact printing than with optical printing). Also, since a new, different piece of film was exposed and printed, matching the exact colors of the original was a problem. Usually the printer work was limited to only the parts of a dissolve needing the effect. The original footage was spliced mid-shot with the optically-printed portion, often resulting in an obvious change in image quality when the transition occurs.
Other problematic artifacts depend on the effect attempted, most often alignment inaccuracies in matte work. For this reason, shots intended to be manipulated via optical printer were often shot on larger film formats than the rest of the project. Otherwise obsolete formats, such as Vistavision, remained in use for many years after they had been abandoned for the conventional shooting of scenes because their larger frame size provided greater clarity, reduced grain size when reprinted and any alignment problems were not as conspicuous.
- Fielding, Raymond (1972). "7". The Technique of Special Effects Cinematography. Focal Press. ISBN 8038-7031-0 Check
- Couzin, Dennis (1988) "Contact and Optical Printing Sharpness, Some Ultimate Comparisons", Image Technology (Journal of the BKSTS), August 1988, pp=282–284. (online)