A clapperboard is a simple but very important device used in filmmaking. Also referred to as a clapper, slate, or ID, it is typically seen in behind-the-scene photos and videos of movie productions.
It can be an old school device where you write the information on it or an electronic device that features automated, red-lit characters showing the shot information.
There is something more than just the interesting information seen in a clapperboard. Even the clapping movement that creates that distinct sound before the director says “Action!” has a crucial purpose during the filming and editing process.
The clapperboard contains the date, production or film title, name of the director, name of the director of photography, and shot information. The shot information is composed of numbers or a combination of numbers and letters that provide identification on what particular shot is currently being filmed. Although it can be the responsibility of another crew member (especially in independent and low-budget productions where multitasking is usual and there are often fewer crew members on the set), it is ideally the 2nd AC (Assistant Cameraman) who uses the clapperboard.
A verbal identification of the exact shot ID is said aloud by the 2nd AC right after the director says “Camera” and the camera operator says “Rolling” or “Speed.” After this verbal identification, the 2nd AC “claps the clapperboard,” then the director says “Action!” This is the cue for the actor and the rest of the production that the actual filming for the shot just started.
Audio and Video Synchronization
Both the visual and aural cues of the shot information are very important; the main purpose of a clapperboard is to synchronize the visuals with the audio during editing. Long before there were video cameras that allow the video and audio elements to be recorded together, all productions needed to have separate recordings of the visuals and the audio for the film. Even up to now, productions shooting in film format (8mm, 16mm, the more popularly used 35mm, and 65mm films) need separate audio recording equipment to capture live sound on the set.
To ensure that all sound and visual elements match, the editor or his or her assistant uses the clapperboard to know which part of the edit of a particular shot should be used. The shot information is very important to the editor. Without it, the production will waste too much time figuring out where a shot should be placed in the edit. The voice slate makes it easier for the editor to confirm that the separate sound recording is really meant for the shot he or she is trying to synch it with.
By aligning the exact part of the shot of the clapperboard being clapped and the clapping sound, the editor is able to effectively synch the visuals with the audio. Without a clapperboard, he or she will have a hard time synching them using trial and error. This will be a waste of time for the production.
There are some moments when placing a clapperboard is not advisable in a shot, like in a take that requires spontaneous action, shooting a very demanding take where a clapperboard may distract the actor while internalizing the scene, and many other valid reasons. In such cases, an end slate is used. As soon as the shot is recorded, the clapperboard is placed upside down in front of the camera (to indicate that it’s an end slate), the voice slate is mentioned, the clap is made, then the director says “Cut!”