Clapperboard

A clapperboard — sometimes called a clapper, slate, sticks, time slate, marker or several other names — is an important part of the camera department's toolbox used during principal photography. It has several different functions. The information written on it helps to organize the use of the filmed material in post-production. It also synchronizes sound and picture recording by providing an absolute visual and auditory reference point.

Physical description
Typically small, hand-held devices, clappers have two pieces of wood or plastic hinged together so that they can be brought together to make a sharp "clap". This noise is used as an absolute auditory reference for the synchronization of the soundtrack of the scene. On most occasions during the filming of the BBC Wales version of Doctor Who, the board has had the traditional colours of "absolute" white and black, arranged in diagonal slants across the clapping mechanism. These colours are used because they're visible in almost any lighting conditions. However, the production team occasionally use multi-colored clappers.

What's written on a clapper
Typically, clappers in the BBC Wales era have included the series number and the director and director of photography of a scene. Rarely, the producer's name has also been present. Perhaps more crucially, the clapper will contain:
 * a letter designating the camera which produced the shot
 * a slate number (that is, the number assigned to the particular shot)
 * a take number or code
 * the date of filming
 * A number assigned to a roll of film
 * The episode number (by believed broadcast order at the time of filming)
 * The scene number

The clapboard also gives an indication of the basic lighting conditions the scene is supposed to have. The 2AC can choose between "interior" and "exterior", and "day" and "night". This is the only part of the clapboard which doesn't actually indicate the conditions as they are, but actually the conditions as they're supposed to be in the final product. Thus, a shot filmed on an exterior location at noon could be marked with "EXT/NIGHT", if the director of photography is shooting "day for night".

If the scene being shot is one shot by, or having later composition by, the visual effects department, the clapper will be given a code corresponding to a schedule worked out by the production supervisor or her staff. In this way, the visual effects department can better keep track of what special effect shot goes with which principal photography shot.

Who uses the information
Although clapper info is used by a variety of post production departments, it's important to stress the work of three people who are foundational to the information the clappers contain.

The information begins with the writer, whose scripts designate scene numbers. These scene numbers are usually not tampered with, even if certain scenes are cut from the script. Scene numbers that are cut are merely omitted from the later flow of information, without causing a subsequent renumbering of the remaining scenes.

These scene numbers are then written on the clapper, generally underneath the roll number. On Doctor Who the person who physically writes on the clapper is the assistant cameraman. If there are two assistants listed in the credits, the assistant in charge of actually writing the information on the slate will usually be the second one listed — that is, the "2AC". The 2AC is sometimes also called — but never credited on Doctor Who as – the "clapper loader". This title is perhaps more descriptive of the actual job. Not only does he or she "load the clapper" with information, but he or she physically loads the camera with film. Thus, he or she is the person most aware of the minutae of the "roll number" — probably the most vital piece of information on the entire clapper. Typically unheralded — and never, as of 2010, included in an interview on Doctor Who Confidential — the 2AC's job is absolutely vital to almost every other department. He or she starts the flow of information to the post-production departments.

His or her counterpart in post is the assistant editor, whose job it is to organize all incoming foootage for the editor. For reasons of efficiency, however, almost all members of the post will organize their planning around the assistant editor's organizational scheme, which in turn is based on the scene number the writer provided in pre-production and the clapper loader gave in production.

Some of the key post-production personnel who depend on the organization the clapperboard naturally brings are the sound design team, the visual effects department, and the colourist.