Synchronizing sound and image

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As pre-striped film is out of production since the mid-1990s (unless you're willing to spend a fortune for getting your unexposed film striped in a dark room), having a separate sound-recorder is the only way to record live-sound...

Synchronizing the camera and the sound-recorder[edit]

Wild sync[edit]

Shooting "wild" (=without sync) is based on the assumption that both the camera and the sound recorder will run at a constant speed for at least 30s. Depending on your devices, you might even have 1min, which should be sufficient for most shots.

Prerequisites: You'll need a clapperboard and a PC with a decent video-editing-program and are willing to pay for a frame-accurate video-transfer.

How do achieve sync: Use the clapperboard at the beginning and the end of each scene. When editing the video you can adjust the sound's length to fit the movements of the clapperboard. (When using a camera and a good recorder, the difference will be so small that the adjustment can be made without changing the sound's pitch.)

Remarks:

  • Some cameras do have a "sync socket" that allows the remote start/stop of a tape-/reel-to-reel-recorder (with some reports that this also works with MiniDisc-recorders with a modified remote-control). When you do have the means to mark the scenes (e.g. by recording silence between the takes), you might even be able to work without a clapperboard.
  • You might shoot the scene simultaneously with a film- and a video-camera. This will give you more clues about the synchrony than just having the sound.

Drawbacks:

  • This method works best with a PC and a video-transfer. (It's possible to use this method with a projector and/or a recorder that can be adjusted in speed, but this will be cumbersome and will most likely end up in a sound with a changed pitch.)
  • This method works best when having a sound-recorder that is either very precise (high-end tape- or reel-to-reel-recorder) or is quartz-controlled (MiniDisc, DAT, DV-camera, WAV-/MP3-recorder, laptop, ...).
  • Having a decent camera and full batteries is a must ;-)
  • You'll need someone to handle the clapperboard and you'll have to waste film to shoot the clapperboard.

Pilot tone (or other signals send from the camera)[edit]

The camera will send one signal per frame. The recorder will either record the signals as beeps on one of its soundtracks or will make a perforated tape run at the camera's speed.

Advantage: This works with any camera having at least a "flash sync"-socket.

Drawbacks:

  • When you don't use perforated tape, you'll "loose" one track to the beeps. As most recorders only do have two tracks (used as left and right for stereophonic sound), you'll end up recording only in mono.
  • You'll either need special equipment (projector, ...) or a frame-accurate video-transfer to sync the sound to the image later on.

Sync-signals send from the recorder to the camera)[edit]

This method is very rare: The recorder produces sync-signals that make the camera run at the recorder's speed.

Drawbacks:

  • This only works with a few cameras and probably even requires a modification of the camera.
  • This only works when the recorder is using the same speed for recording and playback (= you'll most likely need a digital recorder).
  • You'll also need a projector that can adjust its speed to the recorder's signals.

Quartz[edit]

You can select between a variety of digital sound-recorders. All of them are quartz-controlled and hence will run at the same speed upon recording and playback. The only problem is to find a camera that's also quartz-controlled. (Some cameras can be modified, e.g. the ones listed here or the Beaulieu 6008/7008 Pro.) But once you've found such a camera, you'll only need a clapperboard as a reference point to sync the sound and the image in post.

Synchronizing the projector and the sound-recorder[edit]

Projector as a slave[edit]

Having such a projector has got its advantages as it adjusts its speed to signals coming from the recorder. In most cases those signals are audio signals that can also be produced by your PC's soundcard. So you don't have to buy a full sync-sound-system.

Projectors that can be used as a slave for "pulse sync" (list doesn't have to be complete/correct!):

Projector as a master[edit]

As the projector is producing the sync-signals, you'll need a recorder that can adjust its speed to those signals. Unless you want to rely on some special tape- or reel-to-reel-recorders (that are at least 20 years old by now, in most cases even 40 years), you'll have to spend a lot of money to e.g. buy a special CD-player.

You can turn any projector into a master producing sync-signals by measuring it's speed by adding a magnet (to one of its blades) and a reed-contact. Some projectors, e.g. the Elmo ST 1200HD Projector, even have left the factory equipped with such reed-contact.
An alternative method is to turn the projector into a "photoelectric barrier" by putting a sensor in front of the lens. This can normally be done without having the sensor's shadow in the projected image. However this will give you "number of blades"-signals per frame instead of one signal per frame.

Projector running quartz-controlled at a fixed speed[edit]

When the recorder is also quartz-controlled, you'll only have to ensure that both projector and recorder start at the same moment to have sync sound. (In most cases the projector is connected to the recorder's audio-out and will pause until the first louder noise is coming from the recorder.)

Quartz-controlled projectors:

You can turn any "slave projector" (s. above) into a quartz-controlled one by generating the signals with your computer's sound-card (e.g. as described here) or by using one of those devices:

Drawback: As there's no further link between the two devices, they will get immediately out of sync e.g. when the film gets stuck or when the CD hangs.

Links[edit]

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