High motion
From Wikipedia, the free encyclopedia
High motion is the characteristic of video or film footage displayed possessing a sufficiently high frame rate (or field rate) that moving images do not blur or strobe even when tracked closely by the eye. The most common forms of high motion are NTSC and PAL video (ie. "normal television") at their native display rates. Movie film (at the standard 24 fps) does not portray high motion even when shown on television monitors.
Alternate use: In the context of digital video compression, "high motion" is sometimes used to describe footage in which frames change too rapidly for motion prediction techniques to be effective. This article describes only the high frame rate definition.
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[edit] History
In the early 20th century when 35mm movie film was developed, producers found that 18-24 frames per second was adequate for portraying motion in a movie theater environment. Flicker was still a problem at these rates, but projectors solved this by projecting each frame twice, thus creating a refresh rate of 36-48 hz without using excessive amounts of film. However when television was developed, there was no corresponding way to capture a video frame and project it twice. The solution to this was interlace, which had a side effect that a full 50 to 60 images per second were presented to the viewer.
Television producers found that these higher image rates made certain shots possible that were unacceptable on film. Camera pans and text scrolls could be faster. Handheld camera work seemed less objectionable, and most importantly, sports action was much clearer - particularly when following the ball was critical.
[edit] Definition of high motion
There are no commonly used imaging systems that run a rates higher than 30 fps but lower than 48 hz, so 48 hz or higher is the de-facto standard for high motion. The effects of high motion can be reduced or negated by converter lag when NTSC video is converted to PAL, or vice versa (a particular problem for coverage of international sporting events such as the Olympic Games or the FIFA World Cup, for example); however, more recent motion adaptive converters can minimize this. Showscan's research indicates that an average of 66.7 frames per second is the upper limit of what the human eye can perceive, and higher frame rates have no further effect, except in regards to flicker. (see Refresh rate)
[edit] High motion and the "video look"
Until the late 1990s, programs shot on video always possessed high motion, while programming shot on film never did. (The exceptions: Certain motion simulators and amusement park rides included film projected at 48-60 frames per second, and video recorded on Kinescope film recorders lost its high motion characteristic.) This had the result of high motion being associated with news coverage, and low budget programming such as sitcoms or soap operas. Higher budget programming on television was usually shot on film. In the 1950s, when Hollywood experimented with higher frame rates for films (such as with the Todd AO process) some objected to the more video-like look. (Although the inability to convert such films for projection in regular theaters was a more serious problem.)
High motion is often criticized as interfering with the suspension of disbelief, and making it difficult to forget that the viewer is watching actors performing a scene. Some feel that this is an inherent advantage to lower frame rates, while others suggest that it is due to the historical availability of High Motion only in programs that are least able to use the medium artistically, and the evolution of acting techniques based on lack of high motion. In areas where high motion drama is more common, such as Britain, viewers tend to tolerate the look better.
[edit] Effects of new technology
As of the 2000s, digital video technology now makes it possible to shoot video at the "film look" rate of 24 fps at little or no cost. This has resulted in less high motion on television in recent years.
The future presence of digital projectors in theaters opens up the possibility that Hollywood movies could someday include High Motion footage - perhaps in action films intercut with 24 fps for non-action scenes. The MaxiVision48 3-perf film format promotes this use with its ability to switch from 24 fps to 48 fps on the fly during projection. (assuming that a 3 perf projector was use in the theater.) However, 3-perf has not seen much adaptation as a projection format.
