1st Assistant Director (US)
The 1st AD on American productions runs the set on behalf of the Director announcing the takes. When everything is ready for a take (the camera in place, the lights properly set, the actors make-ready, etc.), the 1st AD gives the command to start Sound and Camera ("Sound! Camera!"). Then the director asked the actors to play. The Director then controls the "Cutting" of a take and when it is time to move on to the next scene.
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