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Why must each frame of motion-picture film stop briefly during exposure?

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Director Steven Spielberg and camera operator Michael Chapman film next to a large mechanical shark on the set of the 1975 movie Jaws. — motion-picture technology Director Steven Spielberg holding the movie camera, assisted by camera operator Michael Chapman, during the filming of *Jaws* (1975).

In motion-picture technology, each frame of film must come to a complete, momentary stop during exposure to ensure the recording of a sharp, clear image.12

If the film were moving continuously during the exposure process, the resulting image would be blurred. To achieve the necessary intermittent movement, a mechanical claw or a similar transport system pulls the film into position behind the shutter and locks it in place. While the film is motionless, the shutter opens to expose the frame; the shutter then closes, and the mechanism advances the film to the next frame for the subsequent exposure.1

This stop-and-go process is fundamental to both cameras and projectors. While early devices like the Kinetoscope utilized continuous film movement with very brief, stroboscopic exposures, this method was unsuitable for the bright, enlarged images required for theatrical projection. Consequently, professional filmmaking relies on this intermittent movement to maintain image quality and clarity.2