Clapperboard

A clapperboard, also known as a dumb slate, clapboard, film clapper, film slate, movie slate, or production slate, is a device used in filmmaking and video production to assist in synchronizing of picture and sound, and to designate and mark the various scenes and takes as they are filmed and audio-recorded. It is operated by the clapper loader. It is said to have been invented by Australian filmmaker F. W. Thring. When sound and picture are out of synchronization, lip flap may occur. In the silent era the principal requirement of film stock identification during a day's shoot was the slate. The clapper as two sticks hinged together was invented by F. W. Thring (father of actor Frank Thring), who later became head of Efftee Studios in Melbourne, Australia. The clapperboard with both the sticks and slate together was a refinement of Leon M. Leon (1903–1998), a pioneer sound engineer. The clapperboard combines a chalkboard slate or acrylic board with a set of clapper sticks across the top; one stick is fixed to the upper edge of the slate, while the other is attached to it by a hinge at one end. The slate displays the name of the production, the scene and "take" about to be performed, and similar information; a camera assistant holds the clapperboard so the slate is in view of the cameras with the clapper sticks already open, speaks out information for the benefit of the audio recording, then snaps the sticks shut. The shutting of the clapper sticks is easily identified on the visual track, and the sharp "clap" noise is easily identified on the separate audio track. The two tracks can later be precisely synchronized by matching the sound and movement. Since each take is expressly identified on both the visual and audio tracks, segments of film are easily matched with corresponding segments of audio. It is also known as a "dumb slate". Finding a way to synchronize visual and audio tracks was essential to traditional filmmaking because film stock reacts to light, not sound.