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Encyclopedia > Persistence of vision

According to the theory of persistence of vision, the perceptual processes of the brain or the retina of the human eye retains an image for a brief moment. Persistence of vision is said to account for the illusion of motion which results when a series of film images are displayed in quick succession, rather than the perception of the individual frames in the series. A sketch of the human brain by artist Priyan Weerappuli, imposed upon his sketch of the profile of Michaelangelos David In animals, the brain, or encephalon (Greek for in the head), is the control center of the central nervous system. ... Human eye cross-sectional view. ... Trinomial name Homo sapiens sapiens Linnaeus, 1758 Humans, or human beings, are bipedal primates belonging to the mammalian species Homo sapiens (Latin: wise man or knowing man) under the family Hominidae (the great apes). ... A human eye. ... Film is a term that encompasses individual motion pictures, the field of film as an art form, and the motion picture industry. ...


A visual form of memory known as iconic memory has been described as the cause of this phenomenon[1]. Although psychologists and physiologists have rejected the relevance of this theory to film viewership, film academics and theorists generally have not. Some scientists nowadays consider the entire theory a myth. [1] Iconic memory is a type of short term visual memory, named by George Sperling in 1960. ... A psychologist is a scientist and/or clinician who studies psychology, the systematic investigation of the human mind, including behavior and cognition. ... Physiology (in Greek physis = nature and logos = word) is the study of the mechanical, physical, and biochemical functions of living organisms. ...


Persistence of vision should be compared with the related phenomena of beta movement and phi movement. A critical part of understanding these visual perception phenomena is that the eye is not a camera: there is no "frame rate" or "scan rate" in the eye: instead, the eye/brain system has a combination of motion detectors, detail detectors and pattern detectors, the outputs of all of which are combined to create the visual experience. Beta movement is a perceptual illusion, described by Max Wertheimer in his 1912 Experimental Studies on the Seeing of Motion, whereby two or more still images are combined by the brain into surmised motion. ... The phi phenomenon is a perceptual illusion described by Max Wertheimer in his 1912 Experimental Studies on the Seeing of Motion, in which a disembodied perception of motion is produced by a succession of still images. ... This article or section does not cite its references or sources. ... A camera is a device used to capture images, as still photographs or as sequences of moving images (movies or videos). ... Frame rate, or frame frequency, is the measurement of how quickly an imaging device produces unique consecutive images called frames. ...


The frequency at which flicker becomes invisible is called the flicker fusion threshold, and is dependent on the level of illumination. The flicker fusion threshold (or flicker fusion rate) is a concept in the psychophysics of vision. ...

Contents

Film systems

Through experience in the early days of film innovation, it was determined that a frame rate of less than 16 frames per second caused the mind to see flashing images. Audiences still interpret motion at rates as low as ten frames per second or slower (as in a flipbook), but the flicker caused by the shutter of a film projector is distracting below the 16-frame threshold. Film is a term that encompasses individual motion pictures, the field of film as an art form, and the motion picture industry. ... A flip book is a book with a series of pictures varying gradually from one page to the next, so that when the pages are turned rapidly, the pictures appear to animate, simulating motion or some other change. ... 35 mm Kinoton movie projector in operation. ...


Modern theatrical film runs at 24 frames a second. This is the case for both physical film and digital film systems. Film is a term that encompasses individual motion pictures, the field of film as an art form, and the motion picture industry. ... Digital film refers to cinema production and performance systems which work by using a digital representation of the brightness and colour of each pixel of the image. ...


It is important to distinguish between the frame rate and the flicker rate, which are not necessarily the same. In physical film systems, it is necessary to pull down the film frame, and this pulling-down needs to be obscured by a shutter to avoid the appearance of blurring; therefore, there needs to be at least one flicker per frame in film. To reduce the appearance of flicker, virtually all modern projector shutters are designed to add additional flicker periods, typically doubling the flicker rate to 48 Hz, which is less visible. (Some newer projector shutters even triple it to 72 Hz.) The hertz (symbol: Hz) is the SI unit of frequency. ...


In digital film systems, the scan rate may be decoupled from the image update rate. In some systems, such as the Digital Light Processing (DLP) system, there is no flying spot or raster scan at all, so there is no flicker other than that generated by the temporal aliasing of the film image capture. For political parties using this acronym, see Democratic Labour Party. ... Temporal aliasing is the technical term for a phenomenon also known as the stroboscopic effect or the wagon-wheel effect. ...


The new film system MaxiVision 48 films at 48 frames per second, which, according to film critic Roger Ebert, offers even a strobeless tracking shot past picket fences. The lack of strobe (as opposed to flicker) is due to the higher sampling rate of the camera relative to the speed of movement of the image across the film plane. This ultra-smooth imaging is called High motion. It is critical for sports and motion simulation, but unpopular for drama. Maxivision 24 and Maxivision 48 are 35 mm motion picture film formats, created by Dean Goodhill in 1999. ... Russ Meyer (left) and Roger Ebert, (1970) Roger Joseph Ebert (June 18, 1942 - ) is an Emmy Award-nominated American television personality, author, and film critic who began writing for the Chicago Sun-Times in 1967. ... Jerkiness: In a video display, the perception, by human vision faculties, of originally continuous motion as a sequence of distinct snapshots. ... In motion picture terminology, a tracking shot is the same as a dolly shot or a trucking shot--the camera is mounted on a wheeled platform that is pushed on rails while the picture is being taken. ... The sampling frequency or sampling rate defines the number of samples per second taken from a continuous signal to make a discrete signal. ... 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. ...


Video systems

Video records at 50 (Eurasia) or 60[2] (US & Japan) images per second (ips) depending on the national system used; The flicker or refresh rate on a television screen is fixed to one or the other nationally chosen standards. A technique called interlace uses persistence of vision to combine two consecutive images (or fields) to create one frame with higher detail in non-moving areas. Because the fields are exposed and displayed separately, a single TV "frame" can potentially contain motion or even two distinct images. This is a case of confusing terminology. Video (Latin for I see, first person singular present, indicative of videre, to see) is the technology of electronically capturing, recording, processing, storing, transmitting, and reconstructing a sequence of still images representing scenes in motion. ... Television encoding systems by nation PAL, short for phase-alternating line, phase alternation by line or phase alternation line, is a colour encoding system used in broadcast television systems in large parts of the world. ... The references in this article would be clearer with a different and/or consistent style of citation, footnoting or external linking. ... The refresh rate (or vertical refresh rate, vertical scan rate for CRTs) is the number of times in a second that a display is illuminated. ... For the method of incrementally displaying raster graphics, see Interlace (bitmaps). ...


With ordinary video from video cameras, the flicker rate and the image rate are the same. However, when footage shot on 24 Hz film is shown on 60 Hz TV, each film frame is repeated for 2.5 consecutive fields to produce 60 fields per second. (see 3:2 pulldown) In countries using 50 Hz TV, 24 Fps film is sped up by 4% to produce 25 frames (50 fields) per second.


Some modern video systems also decouple display from image update, for example systems using LCD monitors with continuous light output, or intermediate frame buffers that increase the display rate to 100 or 120 fields per second.


Computer monitors

Computer monitors do not use interlacing. They may sometimes seem to flicker, especially in a brightly lit room. This is due to the greater likelihood that a computer monitor will occupy the viewer's peripheral vision, where sensitivity to flickering is greater. Generally, a refresh rate of 75 Hz or above (as found in most modern monitors) is sufficient to minimize flicker at close viewing distances, and all recent computer monitors are capable of at least that rate. Flat-panel Liquid Crystal Display (LCD) monitors do not suffer from flicker even if their refresh rate is 60 Hz or even lower. This is because LCD pixels open to allow a continuous stream of light to pass through until instructed by the video signal to produce a darker color; see also ghosting. CRTs by comparison create a momentary burst of light each time the electron beam strikes a particular point on the CRT. Nineteen inch (48 cm) CRT computer monitor A computer display, monitor or screen is a computer peripheral device capable of showing still or moving images generated by a computer and processed by a graphics card. ... Reflective twisted nematic liquid crystal display. ... Ghosting can have different meanings: ghosting (television), a double image when receiving a distorted or multipath input signal in analog television broadcasting. ...


Cartoon animation

See Also: Key Frame
This animated cartoon of a galloping horse is displayed at 12 drawings per second, and the fast motion is on the edge of being objectionably jerky. (Assuming your computer has enough system resources for this Animated GIF.)
This animated cartoon of a galloping horse is displayed at 12 drawings per second, and the fast motion is on the edge of being objectionably jerky. (Assuming your computer has enough system resources for this Animated GIF.)

In drawn animation, moving characters are often shot "on twos", that is to say, one drawing is shown for every two frames of film (which usually runs at 24 frames per second), meaning there are only 12 drawings per second. Even though the image update rate is low, the fluidity is satisfactory for most subjects. However, when a character is required to perform a quick movement, it is usually necessary to revert to animating "on ones", as "twos" are too slow to convey the motion adequately. A blend of the two techniques keeps the eye fooled without unnecessary production cost. In animation, key frames (also keyframes) are the drawings which are essential to define a movement. ... Image File history File links Animhorse. ... Image File history File links Animhorse. ... An animated cartoon is a short, hand-drawn (or made with computers to look similar to something hand-drawn) film for the cinema, television or computer screen, featuring some kind of story or plot (even if it is a very short one). ... Horse gaits are the different ways in which a horse can move, either naturally or as a result of specialized training by humans. ... In computing, multitasking is a method by which multiple tasks, also known as processes, share common processing resources such as a CPU. In the case of a computer with a single CPU, only one task is said to be running at any point in time, meaning that the CPU is... GIF (Graphics Interchange Format) is a bitmap image format that is widely used on the World Wide Web, both for still images and for animations. ... Traditional animation, sometimes also called cel animation or hand-drawn animation, is the oldest and historically the most popular form of animation. ...


Animation for most "Saturday morning cartoons" is produced as cheaply as possible, and is most often shot on "threes", or even "fours", i.e. three or four frames per drawing. This translates to only 8 or 6 drawings per second. Saturday morning cartoon is the colloquial term for the animated television programming which was typically scheduled on Saturday mornings on the major American television networks from the 1960s to the 1990s. ...


Printed media

Flip books use this principle. If the book is flipped at a fast enough speed, the illusion of motion is created. A flip book is a book with a series of pictures varying gradually from one page to the next, so that when the pages are turned rapidly, the pictures appear to animate, simulating motion or some other change. ...


Optical toys

Persistence of vision was used to create a number of optical toys that were popular before movies. Most used simple mechanical methods, such as spinning disks or turning spindles, to quickly transpose a series of pictures and so create the illusion of motion. Examples include the zoetrope and the thaumatrope. A modern replica of a Victorian zoetrope. ... A thaumatrope is a toy that was popular in Victorian times. ...


References

  1. ^ Coltheart M. "The persistences of vision." Philos Trans R Soc Lond B Biol Sci. 1980 Jul 8;290(1038):57-69. PMID 6106242.
  2. ^ Actually 59.94, but this is commonly rounded up for discussion.

External links


  Results from FactBites:
 
Persistence of vision - Wikipedia, the free encyclopedia (1128 words)
Persistence of vision is said to account for the illusion of motion which results when a series of film images are displayed in quick succession, rather than the perception of the individual frames in the series.
Persistence of vision should be compared with the related phenomena of beta movement and phi movement.
Persistence of vision does not work at such a low image rate, and the motion may be objectionably jerky.
  More results at FactBites »

 
 

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