Movie Making Manual/Slate

This Module is part of the Movie Making Manual

The clapper board (AKA Clap slate) is a well-recognized icon of filming and the filming industry, but serves many purposes beyond its appearance. A clapper board is made up of two parts: the slate and the clapper.

The slate's most obvious purpose is the documentation it provides on what scene is being filmed, when it was filmed, what take it was, which film reel it was, etc. The "clapper" provides an easily identified audio marker, which is useful when filming with multiple cameras and you must synchronize them during post-production, and is more commonly used to synchronize the sound and picture since they are usually recorded on separate devices. The black-and-white stripes on the clapper are designed to show exactly when the clapper is closed. This point is then synchronised with the sound of the 'clap' it makes.

Increasingly in the modern digital age, the clapper becomes less useful as footage can be digitally marked by the camera and audio synchronization is no longer a problem due to the digital nature of the footage. However, for the sake of your editor, you may wish to continue using a clapper to make any possible problem easier to fix.

How To Use a Clapper Board


While a clapper board seems simple, its use is more complex than it looks. When motion picture film is developed, the lab technician who is developing the film, printing the film, and syncing the audio to the film, must have all the necessary information to sync the audio to the picture. If you want to see your dailies the first thing in the morning and you want everything to work properly, you must never confuse the lab technician.

Verbal Slate


While the clapper board provides information for the picture, there must also be a verbal slate for the audio. This verbal slate must provide the scene and take number for the lab technician. It also usually includes the name of the production and or episode if its for TV. The verbal slate must also make it clear if multiple cameras are used. The verbal slate must also make it clear if multiple tracks of audio are used. "Stereo Split" means one track of a stereo track has the audio from one microphone and the other track has audio from the other microphone.

In film production a letter is generally added to the end of a scene number to designate a change in the camera. This change can be, a lens, a camera move or an angle change. It is also common practice to use the phonetic alphabet when verbalizing the information on the slate. Sometimes the number of angles requires more than the alphabet can provide and in this case, double letters are used.

A and B Cameras


If there are two or more cameras, sometimes a common slate is used. Both the slate and the verbal slate must make this clear.

Using a common slate is not good because it can be confusing. With a common slate, there is no camera number ("Camera A" vs. "Camera B') and no film reel number. Therefore, each camera should have its own slate. The slate information for one camera must never be seen by the other camera. The same rule applies for showing the clapper closing. Therefore, when one camera is slated, someone puts their hand over the lens of the other camera to block the view of the other camera's slate.

Tail Slates


Sometimes, when it is impossible to use a clapper board at the beginning of a shot, someone will yell "Tail Slate" at the beginning of the shot and at the end of the shot, the slate will be clapped upside down so that the film laboratory will know that this is the slate at the end of a shot rather than the slate for the beginning of the next shot. The verbal slate is always done at the same time as the clapper board.

Any Pulse Will Do


On shots where a clapper board is not practical, the actors will use their arms as a huge clapper. The film lab can easily see when the actor's hands come together. This noise is loud enough and concentrated enough to be accurate for syncing the audio to the picture.



If there is no clapper for a shot, then the sound is wild. The lab technician might try to do a rough sync. Or the technician will create a separate section of the dailies for the audio from wildtracks. When you hear a wild track on the dailies, you see only a card saying Wildtrack as you hear the audio.

Re-syncing Sound


For motion picture film, the closing of the clapper (as seen on the film) must be aligned with the audio pulse (which shows up on the audio tape as a blip). Since audio travels at about 40 feet/13.8 meters per frame of motion picture film (1/24th of a second), the audio pulse should be less than one frame after the closing of the slate unless the microphone is far from the camera (and the audience.) Yet, when you watch dailies made using digital slates in Hollywood, you will find that most film labs sync the audio so it is late by one or two frames because the electronics in the slate are slow. Therefore, before you begin editing your movie, you must resync each take based on the actual clapper closing and the pulse on the audio track.

DV Camcorders


DV Camcorders often are supplemented with a separate audio recording device in order to record better sound quality. In this case it is necessary to use a clapper in the beginning (or at the end if you are tailslating) in order to sync the sound up with the video.

Executing the Slate


There are three important parts to execution of the slate.

  1. The information on the slate needs to be readable. This means the handwriting is a factor and letters should be bold, large, clear and in the best focus as possible. With dry erase type slates, a black marker is the best color to use because of the high contrast.
  2. The clapper must close while in frame. The operator should take notice to hold the slate steady. The upper portion of the clapper should be the only thing moving. This helps during the sound syncing process so that it makes it very clear when the slate is closed, as there will generally be motion blur while the upper portion of the clapper is moving. The board needs to be held so that the information is not obstructed by the person holding it.
  3. The audio of the take number and the sound of the slate closing must be clearly recorded. Background noise should be kept at a minimum.

The first and second portions don't have to occur at the same time but the second and third MUST.

It is common to hold the information portion of the slate in frame then back up to get the clapper closing in frame. Optionally, A pocket-sized version of the slate can be used if there isn't room for the entire slate to fit in frame. The pocket-sized version is usually only the slate portion of the unit. Also, the clapper portion of the slate, although rarely removable, can be used separately as well. Three-foot-long versions of a clapper are available for extreme wide shots that need to sync sound and the operator must be a good distance from the camera.

When using the slate near actorS, it is common courtesy to add to the call, "soft sticks" and close the slate more softly so that the actors' hearing is not effected. The clapper closing can be quite loud and creates a very large spike on the audio, which is why it's used.

On set there are calls that occur to let everyone know filming is about to begin. When the 1st AD calls picture up, it's best for the slate operator (2nd Assistant Camera) to already know where he will be executing the slate. This should be with the slate portion in frame with the clapper up and ready to go. The camera should be aiming at the slate when they start the film so that the slate can be the first image seen on the take (even more helpful to editors in the digital process). The camera(s) will give a call of "rolling" and sound will give a call of "speeding" at which time the operator will be told to "mark it". The operator then says the name of the film, the scene number with letter designation, the take number, and "marker" then closes the slate. If it wasn't clear, the sound or camera operator might ask for "second sticks", in which case the slate operator would open the clapper and start again. This will be repeated until everyone is satisfied with what's on camera and sound.

In low-light situations it may be required to shine a light on the slate so that it's visible on camera.

MOS (with out sound)


Although the origin of MOS is debated, recording picture without sound happens often. It is common practice to leave the clapper portion closed and put two fingers over the clapper portion of the slate to indicate that no sound is being recorded.

Watch Dailies


If you want to see how the clapper board is used, simply look at film dailies from motion pictures and television dramas. You can buy motion picture and television drama dailies on tape at almost any second-hand video store in Hollywood (Southern California residents only).

See Also