Jerkiness (sometimes calledstrobing orchoppy footage) describes the perception of individualstill images while watching amotion picture.[1]
Motion pictures are made from still images shown in rapid sequence. Provided there is sufficient continuity between the images and provided the sequence is shown fast enough, thecentral nervous system interprets the sequence as continuous motion. However, some technologies cannot process or carry data fast enough for sufficiently highframe rates. For example, viewing motion pictures byInternet connection generally necessitates a greatly reduced frame rate, making jerkiness clearly apparent.
In conventionalcinematography, the images are filmed and displayed at 24 frames per second, at which speed jerkiness is not normally discernible.Television screensrefresh at even higherfrequencies.PAL andSÉCAM television (the standards inEurope) refresh at 25 or 50 (HDTV) frames per second.NTSC television displays (the standard inNorth America) refresh at 29.97 frames per second.Animated cartoon films are typically made at reduced frame rates (accomplished by shooting severalfilm frames of the individual drawings) so as to limit production costs, with the result that jerkiness tends to be apparent, especially on olderlimited animation features.[2]
Strobing can also refer tocross colour andMoiré patterning. Cross colour refers to when any high frequency luminance content of the picture, close to the TV system's colour sub-carrier frequency, is interpreted by the analogue receiver's decoder as colour information. Moiré patterning is where an interference pattern is produced by fine scene detail beating with the line (or evenpixel) structure of the device used to analyse or display the scene.
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