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Our problem was how to establish accurate start marks — i.e., some recog¬ nizable identification to precede the be¬ ginning of the playback music, and a corresponding, time-identification on the film to facilitate synchronizing both picture and sound at the editing table.
Our first step was to transfer the music on the disc to 16mm magnetic film, using a synchronous magnetic film recorder. In this way we provided the essential element of synchronization — a steady, uniform rate of travel of the sound medium to match the uniform speed of the film moving through the camera. Both the recorder and the cam¬ era were driven by sync motors.
With both the picture film and the sound film now set to move at uniform speeds, the next step was to provide the start or “sync” marks. We hit upon a simple method which utilizes a flash bulb for making the sync mark on the picture film, and employs a small piece of tinfoil as the sync mark on the sound film. The latter triggers the firing of the flash bulb, which over-exposes a single frame of the negative for the pic¬ ture sync mark. The firing of the flash bulb is shown in the composite photo (Fig. 1). As the camera starts filming the three ballerinas (inset photo), the magnetic recorder (off-stage) causes the flash bulb to ignite.
The sound film cue mark is a l/o-inch piece of tinfoil attached to the film with Scotch tape 24 frames in advance of the music, which is the standard sound track advance over picture. The tinfoil segment on the sound film bridges the electrical terminals of the flash system as it passes over them and, being an electrical conductor, closes the circuit and causes the flash bulb to ignite — as shown in the diagram Fig. 2.
The arrangement is shown pictorially in Fig. 3. Here the segment of tin foil rests against the two spring steel con¬ tacts, which press lightly against the base side of the magnetic film. Figure 4 shows the work print of the picture film and sound track film locked in the synchronizer, with arrows pointing to the corresponding start marks. Match¬ ing the work print cue mark (flashframe) with the sound track (tin foil) assures that both will remain in sync throughout the editing procedure.
It should be emphasized that elec¬ tronic flash cannot be used successfully in this flash-frame method of start¬ marking the picture film. This is be¬ cause the electronic flash has a dura¬ tion of but 1/lOOOth of a second against that of about I /25th second for the flash bulb.
It is also recommended that a 221/2or 45-volt battery be used to deliver the strong electrical surge required in firing the flash bulb. end
FIG. 3 — Arrow points to the two spring steel terminals mounted in film path of StancilHoffman synchronous magnetic 16mm film recorder. Here the tin-foil segment is shown bridging the two terminals which closes the electrical circuit and ignites the flash bulb.
FIG. 4 — Arrows point to the tin foil segment attached to the 16mm magnetic sound film, also the flash on the 35mm picture film. Both films are locked in sync in the synchronizer, ready for editing.
American Cinematocrapher
October, 1956
601