Jerkiness
Encyclopedia
Jerkiness, sometimes called strobing, describes the perception of individual still images in a motion picture.
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, the central nervous system
interprets the sequence as continuous motion.
In conventional cinematography
, the images are filmed and displayed at 24 frames per second, at which speed jerkiness is not normally discernible.
Television screens refresh
at even higher frequencies
. PAL
and SÉCAM
television (the standards in Europe
) refresh at 25 or 50 (HDTV) frames per second. NTSC
television displays (the standard in North America
) refresh at 29.97 frames per second.
However, some technologies cannot process or carry data fast enough for sufficiently high frame rate
s. For example, viewing motion pictures by Internet
connection generally necessitates a greatly reduced frame rate, making jerkiness clearly apparent.
Animated cartoon
films are typically made at reduced frame rates (accomplished by shooting several film frame
s of the individual drawings) so as to limit production costs, with the result that jerkiness tends to be apparent.
Strobing can also refer to cross colour and Moiré patterning
:
The former is where any high frequency luminance content of the picture, close to the TV systems colour sub-carrier frequency, is interpreted by the analogue receiver's decoder as colour information.
Moiré
is where an interference pattern is produced by fine scene detail beating with the line (or even pixel
) structure of the device used to analyse or display the scene.
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, the central nervous system
Central nervous system
The central nervous system is the part of the nervous system that integrates the information that it receives from, and coordinates the activity of, all parts of the bodies of bilaterian animals—that is, all multicellular animals except sponges and radially symmetric animals such as jellyfish...
interprets the sequence as continuous motion.
In conventional cinematography
Cinematography
Cinematography is the making of lighting and camera choices when recording photographic images for cinema. It is closely related to the art of still photography...
, the images are filmed and displayed at 24 frames per second, at which speed jerkiness is not normally discernible.
Television screens refresh
Refresh rate
The refresh rate is the number of times in a second that a display hardware draws the data...
at even higher frequencies
Frequency
Frequency is the number of occurrences of a repeating event per unit time. It is also referred to as temporal frequency.The period is the duration of one cycle in a repeating event, so the period is the reciprocal of the frequency...
. PAL
PAL
PAL, short for Phase Alternating Line, is an analogue television colour encoding system used in broadcast television systems in many countries. Other common analogue television systems are NTSC and SECAM. This page primarily discusses the PAL colour encoding system...
and SÉCAM
SECAM
SECAM, also written SÉCAM , is an analog color television system first used in France....
television (the standards in Europe
Europe
Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...
) refresh at 25 or 50 (HDTV) frames per second. NTSC
NTSC
NTSC, named for the National Television System Committee, is the analog television system that is used in most of North America, most of South America , Burma, South Korea, Taiwan, Japan, the Philippines, and some Pacific island nations and territories .Most countries using the NTSC standard, as...
television displays (the standard in North America
North America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...
) refresh at 29.97 frames per second.
However, some technologies cannot process or carry data fast enough for sufficiently high frame rate
Frame rate
Frame rate is the frequency at which an imaging device produces unique consecutive images called frames. The term applies equally well to computer graphics, video cameras, film cameras, and motion capture systems...
s. For example, viewing motion pictures by Internet
Internet
The Internet is a global system of interconnected computer networks that use the standard Internet protocol suite to serve billions of users worldwide...
connection generally necessitates a greatly reduced frame rate, making jerkiness clearly apparent.
Animated cartoon
Animated cartoon
An animated cartoon is a short, hand-drawn film for the cinema, television or computer screen, featuring some kind of story or plot...
films are typically made at reduced frame rates (accomplished by shooting several film frame
Film frame
In filmmaking, video production, animation, and related fields, a film frame or video frame is one of the many still images which compose the complete moving picture...
s of the individual drawings) so as to limit production costs, with the result that jerkiness tends to be apparent.
Strobing can also refer to cross colour and Moiré patterning
Moiré pattern
In physics, a moiré pattern is an interference pattern created, for example, when two grids are overlaid at an angle, or when they have slightly different mesh sizes.- Etymology :...
:
The former is where any high frequency luminance content of the picture, close to the TV systems colour sub-carrier frequency, is interpreted by the analogue receiver's decoder as colour information.
Moiré
Moiré pattern
In physics, a moiré pattern is an interference pattern created, for example, when two grids are overlaid at an angle, or when they have slightly different mesh sizes.- Etymology :...
is where an interference pattern is produced by fine scene detail beating with the line (or even pixel
Pixel
In digital imaging, a pixel, or pel, is a single point in a raster image, or the smallest addressable screen element in a display device; it is the smallest unit of picture that can be represented or controlled....
) structure of the device used to analyse or display the scene.