MOS (film)
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MOS is a standard motion picture jargon abbreviation, used in production reports to indicate an associated film segment has no synchronous audio track.
Omitting sound recording from a particular shot can save time and relieve the film crew of certain requirements, such as remaining silent during a take, and thus MOS takes are common on film shoots, most obviously when the subjects of the take are not speaking or otherwise generating useful sound.
[edit] Origins of the Term
The abbreviation "MOS" has many theories on its origin[1]. The mostly likely (or most accepted) seem to be "Motor Only Sync" or "Motor Only Shot."
When sound recording reached the point where the sound was recorded on a synchronized but separate piece of media (such 35mm film, audio tape, or other media) a method of keeping the recording media and camera film "in sync" was needed. The solution was to use a special form of motor which has multiple "windings" in it, and which can be connected to another identical motor in such a way that turning one motor a certain distance will turn the other motor exactly the same distance. The motors did not have to be close together, and, with appropriate circuitry, did not have to be of the same size or power. These motors were called Selsyn (self synchronous) motors. A system was created where a single sound recording room could be connected to any of the stages on a studio lot (you can still see the connection points on some of the oldest stages.) The sound mixer (sound man) on stage connected the control panel to the recording room and the camera. There was a Selsyn motor on the camera and it was linked to a matching Selsyn motor on the sound recording equipment at another point on the studio lot.
In order to use this system, the sound mixer used an intercom to the sound recordist to tell him to, "roll" or start the system. Since this was a very mechanical system, it took some time to start and get up to proper speed. When proper speed and synchronization was reached, the recordist would use the intercom to announce, "Speed" and the Sound Mixer would relay that to the director and crew on the stage. The expression is still used, but now simply means, "Sound is rolling".
It was the recordist who actually started and stopped the camera motor (the camera operator had a switch to ensure that the camera didn't roll at an inopportune time such as loading, replacing lenses, etc., and to stop it if something went amiss). The actual power source for the camera motor was in the Sound Booth.
When a shot was planned that did not require sound, the Sound Mixer would ask the Recordist to, "Roll the Motor Only." The Recordist would start the camera motor without starting the matching "sound" motor and electronics. The procedure acquired the name "Motor Only Shot", thus MOS.
[edit] Alternate Origin
A popular (presumed to be mythical) origin is that MOS stands for either "Mit Out Sprechen" or "Mit Out Sound," a broken-English phrasing meaning "Without sound," as a 1920s German-emigré director might have said it.
According to this theory, a German director, recently transplanted to Hollywood (probably Ernst Lubitsch, but possibly Fritz Lang), was asked by a script supervisor how he would like to shoot the next scene of the day. The director responded "Mit Out Sprechen!", and so this was noted as a joke on the production reports and the camera slates for the shot. This myth ignores the fact that in German the word for "without" is "ohne"; it is highly improbable that a person speaking German as his first language would mistakenly say "mit out" for "without".
[edit] References
While the true origin of MOS may not ever be known, it is important to note that it is indeed posible that MOS can from early German directors. The German word for "with" is Mit and therefore "Mitout sound," or "Mit Out Sound" is feasible.
It should also be noted that "Motor Only Sync," does not specify which motor to roll. So was it the sound motor or the camera motor?
