Clapperboard
Device for synchronizing picture and sound in film production.
A clapperboard—also called a dumb slate, clapboard, film clapper, film slate, movie slate, or production slate—is a tool used in filmmaking, television, and video production to synchronize picture and sound, and to label scenes and takes during filming and audio recording. It is handled by the clapper loader and has become a lasting symbol of the film industry.
In the silent film era, only a slate was needed to identify film stock during a day’s shoot. The clapper—two hinged sticks—is credited to Australian filmmaker F. W. Thring, though it is thought to have been devised by his sound engineers Alan Mill and Harry Whiting. The combination of slate and clapper sticks was later refined by sound engineer Leon M. Leon.
A clapperboard consists of a chalkboard, slate, or acrylic board, with a pair of clapper sticks across the top. One stick is fixed to the slate’s upper edge; the other is hinged at one end so it can move. The slate shows the production name, scene, take, and other details. A camera assistant holds the board so the slate is visible to the cameras, with the sticks open, speaks the information for the audio recording, then snaps the sticks shut. Chalk or dry-erase markers are used to write on the slate or whiteboard. The closing of the sticks is clearly visible on the visual track, and the sharp “clap” is easily heard on the separate audio track, allowing precise synchronization later. Each take is identified on both tracks, making it simple to match film segments with their audio.
Synchronizing visual and audio tracks was essential because film stock reacts to light, not sound. During a shoot, audio was recorded separately on different media (double-system recording). In early sound films, playback was synchronized in post-production with sound-on-disc, then later with sound-on-film. Without a clapperboard, an editor cannot sync footage with audio, as happened with the delayed film *Amazing Grace*. Single-system recording, which recorded sound directly onto film, was later developed for small formats like Super 8, but it did not replace clapperboards. Single-system audio quality is inferior to double-system, and editing is difficult because the sound playback head must be offset from the projector gate, requiring a frame offset (usually 28, 26, or 18 frames ahead). Cutting a shot when an actor stops speaking risks cutting off the last syllable un
- inventor_credited
- F. W. Thring
- field
- Filmmaking, television production, video production
- known_for
- Synchronizing picture and sound, marking scenes and takes
- alternative_names
- Dumb slate, clapboard, film clapper, film slate, movie slate, production slate
Lore & Background
The clapperboard is said to have been invented by Australian filmmaker F. W. Thring, though the invention is thought to be the responsibility of two of his sound engineers: Alan Mill and Harry Whiting. The clapperboard with both the sticks and slate together was a refinement of Leon M. Leon, a pioneer sound engineer. In the silent era, the principal requirement of film stock identification was the slate.
Reader's Guide
The clapperboard is essential for double-system recording, where audio is recorded on separate media from film. The shutting of the clapper sticks provides a visual and audio cue that allows precise synchronization in post-production. Despite the development of single-system recording and videotape, professional film and television productions continue to use clapperboards due to superior audio quality and workflow traditions. Modern digislates incorporate SMPTE timecodes to aid synchronization, but traditional clapper sticks remain necessary in case of timecode drift.
Did You Know?
- The clapperboard is also known as a dumb slate.
- The clapper sticks traditionally have diagonally interleaved lines of black and white to ensure clear visual capture.
- A 'tail slate' or end slate is filmed at the end of a take, with the clapperboard held upside-down.
- Failure to use clapperboards can prevent film editors from synchronizing visual images with audio recordings, as happened with the film Amazing Grace.
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