Slow Motion

bullet time

Slow motion (commonly abbreviated as slowmo) is an effect in film-making whereby time appears to be slowed down. It was invented by the Austrian priest August Musger. Typically this style is achieved when each film frame is captured at a rate much faster than it will be played back.

When replayed at normal speed, time appears to be moving more slowly. A term for creating slow motion film is ‘overcranking’ which refers to hand cranking an early camera at a faster rate than normal (i.e. faster than 24 frames per second). Slow motion can also be achieved by playing normally recorded footage at a slower speed. This technique is more often applied to video subjected to instant replay, than to film.

A third technique that is becoming common is using current computer software post-processing (with programs like Twixtor) is to fabricate digitally interpolated frames to smoothly transition between the frames that were actually shot. Motion can be slowed further by combining techniques, interpolating between overcranked frames. The traditional method for achieving super-slow motion is through high-speed photography, a more sophisticated technique that uses specialized equipment to record fast phenomena, usually for scientific applications.

Slow motion can be used for artistic effect, to create a romantic or suspenseful aura or to stress a moment in time. Vsevolod Pudovkin, for instance, used slow motion in a suicide scene in ‘The Deserter,’ in which a man jumping into a river seems sucked down by the slowly splashing waves. ‘The Matrix’ found success applying the effect to action scenes through the use of multiple cameras, as well as mixing slow-motion with live action in other scenes. Japanese director Akira Kurosawa was a pioneer using this technique in his 1954 movie ‘Seven Samurai.’ American director Sam Peckinpah was another classic lover of the use of slow motion. The technique is especially associated with explosion effect shots and underwater footage.

The opposite of slow motion is fast motion. Cinematographers refer to fast motion as undercranking since it was originally achieved by cranking a handcranked camera slower than normal. It is often used for comic effect, time lapse or occasional stylistic effect. The concept of slow motion may have existed before the invention of the motion picture: the Japanese theatrical form Noh employs very slow movements.

Post production slow motion is referred to as time-stretching or digital slow motion, and is achieved by inserting new frames in between frames that have actually been photographed. Since the necessary frames were never photographed, new frames must be fabricated. Sometimes the new frames are simply repeats of the preceding frames but more often they are created by interpolating between frames. (Often this interpolation is effectively a short dissolve between still frames). Many complicated algorithms exist that can track motion between frames and generate intermediate frames that appear natural and smooth. However it is understood that these methods can never achieve the clarity or smoothness of its overcranking counterpart.

Simple replication of the same frame twice is also sometimes called ‘half-speed.’ This relatively primitive technique (as opposed to digital interpolation) is often visually detectable by the casual viewer. It was used in certain scenes in ‘Tarzan, the Ape Man,’ and critics pointed it out. Sometimes lighting limitations or editorial decisions can require it. A wide-angle shot of Roy Hobbs swinging the bat, in the climactic moments of ‘The Natural,’ was printed at half-speed in order to simulate slow-motion, and the closeup that immediately followed it was true overcranked slow-motion.

The famous bullet-dodging effect popularized by ‘The Matrix’ is referred to as ‘speed ramping’ and is a process whereby the capture frame rate of the camera changes over time. For example, if in the course of 10 seconds of capture, the capture frame rate is adjusted from 60 frames per second to 24 frames per second, when played back at the standard film rate of 24 frames per second, a unique time-manipulation effect is achieved. For example, someone pushing a door open and walking out into the street would appear to start off in slow-motion, but in a few seconds later within the same shot the person would appear to walk in ‘realtime’ (normal speed). The opposite speed-ramping is used in ‘The Matrix’ when Neo re-enters the Matrix for the first time to see the Oracle. As he comes out of the warehouse ‘load-point,’ the camera zooms into Neo at normal speed but as it gets closer to Neo’s face, time seems to slow down, perhaps visually accentuating Neo pausing and reflecting a moment, and perhaps alluding to future manipulation of time itself within the Matrix later on in the movie.

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