well as the costs of certain shots, props, and on-set special effects. When filming begins, the preparation time is over: the final version of the script is done, the cast has been selected, and the buildings and structures on set have largely been completed. The start of filming generally marks a point of no return for the financiers, because until it is complete, there is unlikely to be enough material filmed to release a final product needed to recoup costs. While it is common for a film to lose its greenlight status during the pre-production phase —for example, when an essential cast member drops out or unexpectedly dies, or some scandal engulfs the studio or an actor —it is rare for the film to lose financing once principal photography has begun. Immediately before a take is shot, the scene is rehearsed with camera, light and sound. Most American productions follow a specific procedure: The assistant director (AD) calls "picture is up!" to inform everyone that a take is about to be recorded, and then "quiet, everyone!" Once everyone is ready to shoot, the AD calls "roll sound" (if the take involves sound), and the production sound mixer will start their equipment, record a verbal slate of the take's information, and announce "sound speed", or just "speed", when they are ready. The AD follows with "roll camera", answered by "speed!" by the camera operator once the camera is recording. The clapper, who is already in front of the camera with the clapperboard, calls "marker!" and slaps it shut. If the take involves extras or background action, the AD will cue them ("action background!"), and last is the director, telling the actors "action!". The AD may echo "action" louder on large sets. A take is over when the director calls "Cut!" and the camera and sound stop recording. The ritual helps the general concentration at the location and allows saving costs by only recording the scene rather than the preparation for the scene. Each shot is repeated until the director is satisfied with it. In addition to the actual film crew that does the principal photography (unit), there may be a second team (second unit), which in turn comprises a full film crew with its own director, especially for more complex productions. The second unit works independently but in coordination with the director of the overall project and is responsible for city