Manipulating the Flow of Time
Shooting ‘off-speed’ is a fundamental in-camera technique that allows a filmmaker to manipulate the audience’s perception of time. The standard frame rate for motion pictures is 24 frames per second (fps). This is the speed at which the film is projected in a theater and is the baseline for what we perceive as ‘normal motion.’ ‘Off-speed’ refers to the deliberate choice to set the camera’s recording speed to anything other than this 24 fps standard. By changing the number of frames captured per second, a director can make the action on screen appear to move faster or, more commonly, slower than reality.
Over-Cranking for Slow Motion
The most common use of off-speed filming is to create slow motion. This is achieved by shooting at a frame rate higher than 24 fps—a technique historically called ‘over-cranking.’ For example, if a camera is set to record at 48 fps, it is capturing twice the number of frames in one second of real time. When this footage is played back at the standard 24 fps, the action takes twice as long to unfold, appearing to move at 50% speed. Shooting at even higher frame rates (96 fps, 120 fps, or even over 1,000 fps with specialized cameras) produces even more extreme and dramatic slow-motion effects. This is used to:
- Add emotional weight to a key moment.
- Emphasize the grace or brutality of a physical action.
- Allow the audience to see details that are too fast to perceive in real time, like an explosion or a water splash.
Under-Cranking for Fast Motion
The opposite effect, fast motion, is achieved by shooting at a frame rate lower than 24 fps, known as ‘under-cranking.’ If a scene is shot at 12 fps and played back at 24 fps, the action will appear twice as fast. This technique is often used for comedic effect, creating a jerky, chaotic energy. It can also be used in a more stylized way to show the passage of time, though this is more commonly achieved through time-lapse photography, which is an extreme form of under-cranking.