Clapperboard

A clapperboard is a device used in filmmaking and video production to assist in the synchronizing of picture and sound, and to designate and mark particular scenes and takes recorded during a production. The sharp "clap" noise that the clapperboard makes can be identified easily on the audio track, and the shutting of the clapstick can be identified easily on the separate visual track. The two tracks can then be precisely synchronised by matching the sound and movement. Other names for the clapperboard include clapper, clapboard, clacker, slate, slate board, slapperboard, sync slate, time slate, sticks, board, smart slate, dumb slate and sound marker.

When a movie's sound and picture are out of synchronization, this is known as lip flap.

The clapperboard is the combination of the chalkboard slate that holds information identifying the next scene and the clapstick which is used to align sound and picture. In the early days of film, one person would hold a slate for the camera with the scene information, while another clapped two hinged sticks together in front of the camera. The combination of the two into one unit made it possible for one person to perform both tasks.

Clapperboards have been essential to the filmmaking process since the earliest sound films, since until the advent of digital cinematography, visual and audio tracks were recorded on completely separate media with completely separate equipment by different members of the film crew. If each scene is tagged at the moment of filming with sufficient identifying information in both visual and audio form, then the film editor does not need to waste time guessing which film clips go with which audio recordings.

Traditional clapperboards consisted of a wooden slate and a hinged clapstick attached to the top of the slate. Modern clapperboards generally use a pair of wooden sticks atop whiteboard or translucent acrylic glass slates which do not require additional lighting from the camera side to be legible. Some versions are also backlit. Smart slates or digislates are electronic SMPTE time code versions with LED numbers. The clapsticks traditionally have diagonally interleaved lines of black and white to ensure a clear visual of the clap in most lighting conditions. In recent years sticks with calibrated color stripes have become available. In some productions, particularly those created in the digital domain, electronically superimposed versions of a clapperboard have supplanted the real thing.

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