Slow motion
Slow motion (commonly abbreviated as slow-mo or slo-mo) is an effect in film-making whereby time appears to be slowed down.
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 a slow-motion film is over cranking, which refers to hand cranking an early camera faster than expected (i.e., faster than 24 frames per second). Slow motion can also be achieved by playing usually recorded footage slower. This technique is more often applied to video subjected to instant replay than to film. A third technique uses computer software post-processing to fabricate digitally interpolated frames between the shot frames. Combining techniques can slow motion further, such as 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 is ubiquitous in modern filmmaking. A diverse range of directors uses it to achieve diverse effects. Some classic subjects of slow-motion include:
- Athletic activities of all kinds are used to demonstrate skill and style.
- To recapture a key moment in an athletic game, typically shown as a replay.
- Natural phenomena, such as a drop of water hitting a glass.
Slow motion can also be used for artistic effect, to create a romantic or suspenseful aura, or to stress a moment. Vsevolod Pudovkin, for instance, used slow motion in a suicide scene in his 1933 film The Deserter in which a man jumping into a river seems sucked down by the slowly splashing waves. Another example is Face/Off, in which John Woo used the same technique to move a flock of flying pigeons. The Matrix made a distinct success in applying the effect into action scenes through the use of multiple cameras, as well as mixing slow-motion with live action in other scenes. Japanese director Akira Kurosawa pioneered this technique in his 1954 movie Seven Samurai. American director Sam Peckinpah was another classic lover of slow motion. The method is significantly 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 initially achieved by cranking a hand-cranked camera slower than usual. It is often used for comics or occasional stylistic effects. Extreme fast motion is known as time-lapse photography; a frame of, say, a growing plant is taken every few hours; when the frames are played back at normal speed, the plant is seen to grow before the viewer's eyes.
The concept of slow motion may have existed before the invention of the motion picture: the Japanese theatrical form Noh employs very slow movements.
How slow motion works
There are two ways in which slow motion can be achieved in modern cinematography. Both involve a camera and a projector. A projector refers to a classical film projector in a movie theater, but the same basic rules apply to a television screen and any other device that displays consecutive images at a constant frame rate.
Overcranking
To make the above illustration readable, a projection speed of 10 frames per second (fps) has been selected (the 24 fps film standard makes slow over-cranking rare but available on professional equipment).
Time stretching
The second type of slow motion, time-stretching or digital slow motion, is achieved during post-production. It involves inserting new frames between frames that have already been photographed. The effect is similar to over-cranking, as the actual motion occurs longer.
Since the necessary frames were never photographed, new frames must be fabricated. Sometimes, the new frames repeat the preceding frames, but more often, they are created by interpolating between frames. (Often, this motion interpolation is a short dissolve between still frames.) Many complicated algorithms can track motion between frames and generate intermediate frames within that scene. This is similar to half-speed, and it is not true slow-motion but merely a more extended display of each frame.
In action films
Slow motion is used widely in action films for dramatic effect, as well as the famous bullet-dodging effect popularized by The Matrix. This effect is referred to as speed ramping, which is a process whereby the capture frame rate of the camera changes over time. For example, if in 10 seconds of capture, the capture frame rate is adjusted from 60 frames per second to 24 frames per second, a unique time-manipulation effect is achieved when played back at the standard film rate of 24 frames per second. For example, someone pushing a door open and walking out into the street would appear to start off in slow motion, but a few seconds later, within the same shot, the person would appear to walk in "real-time" (everyday speed). The opposite speed-ramping is done 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. Still, as it gets closer to Neo's face, time seems to slow down, perhaps visually accentuating Neo's pausing and reflecting a moment and perhaps alluding to future manipulation of time itself within the Matrix later on in the movie.
In broadcasting
Slow-motion is widely used in sport broadcasting and its origins in this domain extend back to the earliest days of television, one example being the European Heavyweight Title in 1939 where Max Schmeling knocked out Adolf Heuser in 71 seconds.
HS-100 at DC Video
In instant replays, slow-motion reviews are now commonly used to show in detail some action (photo finish, goal, ...). Generally, they are made with video servers and special controllers. The first TV slo-mo was the Ampex HS-100 disk record player. After the HS-100, Type C videotape VTRs with a slow-motion option were used. There were a few special high-frame rate TV systems (300 fps) made to provide higher quality slow-motion for TV. 300 fps can be converted to 50 and 60 fps transmission formats without major issues.
- More information is available at [ Wikipedia:Slow_motion ]
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