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Persistence of vision traditionally refers to the optical illusion that occurs when visual perception of an object does not cease for some time after the rays of light proceeding from it have ceased to enter the eye. The illusion has also been described as "retinal persistence", "persistence of impressions", simply "persistence" and other variations. A very commonly given example of the phenomenon is the apparent fiery trail of a glowing coal or burning stick while it is whirled around in the dark. Many explanations of the illusion actually seem to describe either positive afterimages or
motion blur Motion blur is the apparent streaking of moving objects in a photograph or a sequence of frames, such as a film or animation. It results when the image being recorded changes during the recording of a single exposure, due to rapid movement or lo ...
. "Persistence of vision" can also be understood to mean the same as " flicker fusion," the effect that vision seems to persist continuously when the light that enters the eyes is interrupted with short and regular intervals. When the frequency is too high for the
visual system The visual system comprises the sensory organ (the eye) and parts of the central nervous system (the retina containing photoreceptor cells, the optic nerve, the optic tract and the visual cortex) which gives organisms the sense of sight (th ...
to discern differences between moments, light and dark impressions fuse together into a continuous impression of the scene with intermediate brightness. Since its introduction, the term "persistence of vision" has been believed to be the explanation for
motion perception Motion perception is the process of inferring the speed and direction of elements in a scene based on visual, vestibular and proprioceptive inputs. Although this process appears straightforward to most observers, it has proven to be a difficult ...
in
optical toys Optical toys form a group of devices with some entertainment value combined with a scientific, optical nature. Many of these were also known as "philosophical toys" when they were developed in the 19th century. People must have experimented with op ...
like the
phenakistiscope The phenakistiscope (also known by the spellings phénakisticope or phenakistoscope) was the first widespread animation device that created a fluent illusion of motion. Dubbed and ('stroboscopic discs') by its inventors, it has been known und ...
and the
zoetrope A zoetrope is one of several pre-film animation devices that produce the illusion of motion by displaying a sequence of drawings or photographs showing progressive phases of that motion. It was basically a cylindrical variation of the phénak ...
, and later in cinema. However, this theory has been disputed even before cinematography's breakthrough in 1895. If "persistence of vision" is explained as "flicker fusion", it can be regarded as the reason why the dark intervals don't interrupt the continuous impression of a depicted scene. The illusion of motion as a result of fast intermittent presentations of sequential images is a
stroboscopic effect The stroboscopic effect is a visual phenomenon caused by aliasing that occurs when continuous rotational or other cyclic motion is represented by a series of short or instantaneous samples (as opposed to a continuous view) at a sampling rate c ...
, as detailed by inventor
Simon Stampfer Simon Ritter von Stampfer (26 October 1792 (according to other sources 1790)), in Windisch-Mattrai, Archbishopric of Salzburg today called Matrei in Osttirol, Tyrol – 10 November 1864 in Vienna) was an Austrian mathematician, surveyor and ...
. Early descriptions of the illusion often attributed the effect purely to the
physiology Physiology (; ) is the scientific study of functions and mechanisms in a living system. As a sub-discipline of biology, physiology focuses on how organisms, organ systems, individual organs, cells, and biomolecules carry out the chemic ...
of the eye, particularly of the
retina The retina (from la, rete "net") is the innermost, light-sensitive layer of tissue of the eye of most vertebrates and some molluscs. The optics of the eye create a focused two-dimensional image of the visual world on the retina, which the ...
. Nerves and parts of the brain later became accepted as important factors.
Sensory memory During every moment of an organism's life, sensory information is being taken in by sensory receptors and processed by the nervous system. Sensory information is stored in sensory memory just long enough to be transferred to short-term memory. H ...
has been cited as a cause.


Natural occurrences and applications

Some natural phenomena and the principles of some optical toys have been attributed to the persistence of vision effect. Patrick d'Arcy recognised the effect in "the luminous ring that we see by turning a torch quickly, the fire wheels in the fireworks, the flattened spindle shape we see in a vibrating cord, the continuous circle we see in a cogwheel that turns with speed". Basically everything that resembles motion blur seen in fast moving objects could be regarded as "persistence of vision".


Sparkler's trail effect

The apparent line of light behind a fast moving luminous object is known as the "sparkler's trail effect", since it is commonly known from the use of
sparkler A sparkler is a type of hand-held firework that burns slowly while emitting bright, intense colored flames, sparks, and other effects. Sparklers are particularly popular with children. In the United Kingdom, a sparkler is often used by chil ...
s. The effect has occasionally been applied in the arts by writing or drawing with a light source recorded by a camera with a long exposure time.


Color-top / Newton disc

Colors on spinning tops or rotating wheels mix together if the motion is too fast to register the details. A colored dot then appears as a circle and one line can make the whole surface appear in one uniform hue. The Newton disc optically mixes wedges of
Isaac Newton Sir Isaac Newton (25 December 1642 – 20 March 1726/27) was an English mathematician, physicist, astronomer, alchemist, Theology, theologian, and author (described in his time as a "natural philosophy, natural philosopher"), widely ...
's primary colors into one (off-)white surface when it spins fast.


Thaumatrope

In April 1825 the first ''
Thaumatrope A thaumatrope is an optical toy that was popular in the 19th century. A disk with a picture on each side is attached to two pieces of string. When the strings are twirled quickly between the fingers the two pictures appear to blend into one due t ...
'' was published by W. Phillips (in anonymous association with
John Ayrton Paris John Ayrton Paris, FRS (178524December 1856) was a British physician. He is most widely remembered as a possible inventor of the thaumatrope, which he published with W. Phillips in April 1825. Life Paris was a medical researcher of distinctio ...
). The fact that the pictures on either side of the twirling disc seem to blend together into one image has often been used to illustrate the concept of persistence of vision.


Kaleidoscopic colour-top

In April 1858 John Gorham patented his ''Kaleidoscopic colour-top''. This is a top on which two small discs are placed, usually one with colors and a black one with cut-out patterns. When the discs spin and the top disc is retarded into regular jerky motions the toy exhibits "beautiful forms which are similar to those of the kaleidoscope" with multiplied colours. Gorham described how the colours appear mixed on the spinning top "from the duration of successive impressions on the retina". Gorham founded the principle on "the well-known experiment of whirling a stick, ignited at one end" (a.k.a. the sparkler's trail effect).


Rubber pencil trick

A pencil or another rigid straight line can appear as bending and becoming rubbery when it is wiggled fast enough between fingers, or otherwise undergoing rigid motion. Persistence of vision has been discarded as sole cause of the illusion. It is thought that the eye movements of the observer fail to track the motions of features of the object. This effect is widely known as an entertaining "magic" trick for children.


LED POV displays

The term "persistence of vision display" or "POV display" has been used for LED display devices that compose images by displaying one spatial portion at a time in rapid succession, (for example, one column of pixels every few milliseconds). A two-dimensional POV display is often accomplished by means of rapidly moving a single row of LEDs along a linear or circular path. The effect is that the image is perceived as a whole by the viewer as long as the entire path is completed during the visual persistence time of the human eye. A further effect is often to give the illusion of the image floating in mid-air. A three-dimensional POV display is often constructed using a 2D grid of LEDs which is swept or rotated through a volume. POV display devices can be used in combination with long camera exposures to produce
light writing Light writing is an emerging form of stop motion animation wherein still images captured using the technique known as light painting or light drawing are put in sequence thereby creating the optical illusion of movement for the viewer. Techniq ...
. A common example of this can be seen in the use of bicycle wheel lights that produce patterns.


History

Phenomena related to flicker fusion and motion blur have been described since antiquity. Film historians have often confused flicker fusion with afterimages that arise after staring at an object, while mostly ignoring the importance of the stroboscopic effect in their explanations of motion perception in film.


Historical references to afterimages

Aristotle (384–322 BC) noted that the image of the sun remained in his vision after he stopped looking at it. The discovery of persistence of vision is sometimes attributed to the Roman poet
Lucretius Titus Lucretius Carus ( , ;  – ) was a Roman poet and philosopher. His only known work is the philosophical poem '' De rerum natura'', a didactic work about the tenets and philosophy of Epicureanism, and which usually is translated into E ...
(c. 15 October 99 BC – c. 55 BC), although he only mentions something similar in connection with images seen in a dream. Around 165 AD
Ptolemy Claudius Ptolemy (; grc-gre, Πτολεμαῖος, ; la, Claudius Ptolemaeus; AD) was a mathematician, astronomer, astrologer, geographer, and music theorist, who wrote about a dozen scientific treatises, three of which were of importanc ...
described in his book ''
Optics Optics is the branch of physics that studies the behaviour and properties of light, including its interactions with matter and the construction of instruments that use or detect it. Optics usually describes the behaviour of visible, ultrav ...
'' a rotating potter's wheel with different colors on it. He noted how the different colors of sectors mixed together into one color and how dots appeared as circles when the wheel was spinning very fast. When lines are drawn across the axis of the disc they make the whole surface appear to be of a uniform color. "The visual impression that is created in the first revolution is invariably followed by repeated instances that subsequently produce an identical impression. This also happens in the case of shooting stars, whose light seems distended on account of their speed of motion, all according to the amount of perceptible distance it passes along with the sensible impression that arises in the visual faculty." Porphyry (circa 243–305) in his commentary on Ptolemy's ''Harmonics'' describes how the senses are not stable but confused and inaccurate. Certain intervals between repeated impressions are not detected. A white or black spot on a spinning cone (or top) appears as a circle of that color and a line on the top makes the whole surface appear in that color. "Because of the swiftness of the movement we receive the impression of the line on every part of the cone as the line moves." In the 11th century
Ibn al-Haytham Ḥasan Ibn al-Haytham, Latinized as Alhazen (; full name ; ), was a medieval mathematician, astronomer, and physicist of the Islamic Golden Age from present-day Iraq.For the description of his main fields, see e.g. ("He is one of the pr ...
, who was familiar with Ptolemy's writings, described how colored lines on a spinning top could not be discerned as different colors but appeared as one new color composed of all of the colors of the lines. He deducted that sight needs some time to discern a color. al-Haytam also noted that the top appeared motionless when spun extremely quickly "for none of its points remains fixed in the same spot for any perceptible time".
Leonardo da Vinci Leonardo di ser Piero da Vinci (15 April 14522 May 1519) was an Italian polymath of the High Renaissance who was active as a painter, draughtsman, engineer, scientist, theorist, sculptor, and architect. While his fame initially rested on ...
wrote in a notebook: "Every body that moves rapidly seems to colour its path with the impression of its hue. The truth of this proposition is seen from experience; thus when the lightning moves among dark clouds the speed of its sinuous flight makes its whole course resemble a luminous snake. So in like manner if you wave a lighted brand its whole course will seem a ring of flame. This is because the organ of perception acts more rapidly than the judgment." In his 1704 book ''
Opticks ''Opticks: or, A Treatise of the Reflexions, Refractions, Inflexions and Colours of Light'' is a book by English natural philosopher Isaac Newton that was published in English in 1704 (a scholarly Latin translation appeared in 1706). (''Optic ...
'',
Isaac Newton Sir Isaac Newton (25 December 1642 – 20 March 1726/27) was an English mathematician, physicist, astronomer, alchemist, Theology, theologian, and author (described in his time as a "natural philosophy, natural philosopher"), widely ...
(1642–1726/27) described a machine with prisms, a lens and a large moving comb with teeth causing alternating colors to be projected successively. If this was done quickly enough, the alternating colours could no longer be perceived separately but were seen as white. Newton compared its principle to the sparkler's trail effect: a gyrating burning coal could appear as a circle of fire because "the sensation of the coal in the several places of that circle remains impress'd on the sensorium, until the coal return again to the same place." In 1768
Patrick d'Arcy Patrick d'Arcy (27 September 1725 – 18 October 1779) was an Irish mathematician born in Kiltullagh, County Galway in the west of Ireland. His family, who were Catholics, suffered under the penal laws. In 1739 d'Arcy was sent abroad b ...
(1725-1779) reported how he had measured a duration of 0.13 seconds for one full rotation of a burning coal while it was seen as a full circle of light. He registered multiple rotations with a purpose-built machine in his garden and with the collaboration of an observer who had superior eyesight (D'Arcy's own eyesight had been damaged in an accident). D'Arcy suspected that the duration may differ between different observers, light intensities of spinning objects, colours and viewing distances. He planned further experiments to determine such possible differences,d’Arcy, Patrick ''Sur la durée de la sensation de la vue'' in ''Histoire de l'Académie Royale des Sciences - Année M. DCCXV.'' p. 439-451 (1768) https://books.google.com/books?id=cL5eAAAAcAAJ&pg=RA1-PA439 but no results seem to have been published.


1820–1866: Revolving wheel

In 1821 the ''Quarterly Journal of Science, Literature, and The Arts'' published a "letter to the editor" with the title ''Account of an Optical Deception.'' It was dated Dec. 1, 1820 and attributed to "J.M.", possibly publisher/editor John Murray himself. The author noted that the spokes of a rotating wheel seen through fence slats appeared with peculiar curvatures (see picture). The letter concluded: "The general principles on which this deception is based will immediately occur to your mathematical readers, but a perfect demonstration will probably prove less easy than it appears on first sight". Four years later
Peter Mark Roget Peter Mark Roget ( ; 18 January 1779 – 12 September 1869) was a British physician, natural theologian, lexicographer and founding secretary of The Portico Library. He is best known for publishing, in 1852, the '' Thesaurus of English Word ...
offered an explanation when reading at the
Royal Society The Royal Society, formally The Royal Society of London for Improving Natural Knowledge, is a learned society and the United Kingdom's national academy of sciences. The society fulfils a number of roles: promoting science and its benefits, re ...
on December 9, 1824. He added: "It is also to be noticed that, however rapidly the wheel revolves, each individual spoke, during the moment it is viewed, appears to be at rest." Roget claimed that the illusion is due to the fact "that an impression made by a pencil of rays on the retina, if sufficiently vivid, will remain for a certain time after the cause has ceased." He also provided mathematical details about the appearing curvatures. As a university student
Joseph Plateau Joseph Antoine Ferdinand Plateau (14 October 1801 – 15 September 1883) was a Belgian physicist and mathematician. He was one of the first people to demonstrate the illusion of a moving image. To do this, he used counterrotating disks with repe ...
noticed in some of his early experiments that when looking from a small distance at two concentric cogwheels which turned fast in opposite directions, it produced the optical illusion of a motionless wheel. He later read Peter Mark Roget's 1824 article and decided to investigate the phenomenon further. He published his findings in ''Correspondance Mathématique et Physique'' in 1828 and 1830. In 1829 Plateau presented his then unnamed anorthoscope in his doctoral thesis ''Sur quelques propriétés des impressions produites par la lumière sur l'organe de la vue''. The anorthoscope was a disc with an anamorphic picture that could be viewed as a clear immobile image when the disc was rotated and seen through the four radial slits of a counter-rotating disc. The discs could also be translucent and lit from behind through the slits of the counter-rotating disc. On 10 December 1830, scientist
Michael Faraday Michael Faraday (; 22 September 1791 – 25 August 1867) was an English scientist who contributed to the study of electromagnetism and electrochemistry. His main discoveries include the principles underlying electromagnetic inducti ...
wrote a paper for the ''Journal of the
Royal Institution The Royal Institution of Great Britain (often the Royal Institution, Ri or RI) is an organisation for scientific education and research, based in the City of Westminster. It was founded in 1799 by the leading British scientists of the age, inc ...
of Great Britain'', entitled ''On a Peculiar Class of Optical Deceptions''. Two instances of rotating wheels that appeared to stand still had been pointed out to him and he had read about the somewhat similar palisade illusion in Roget's article. Faraday started experimenting with rotations of toothed cardboard wheels. Several effects had already been described by Plateau, but Faraday also simplified the experiment by looking at a mirror through the spaces between the teeth in the circumference of the cardboard disc. On 21 January 1831, Faraday presented the paper at the Royal Institution, with some new experiments. He had cut concentric series of apertures nearer to the center of a disc (representing smaller cogwheels) with small differences in the amount of "cogs" per "wheel". When looking at the mirror through the holes of one of the wheels in the rotating disc, that wheel seemed to stand still while the others would appear to move with different velocities or opposite direction. Plateau was inspired by Faraday's additional experiments and continued the research. In July 1832 Plateau sent a letter to Faraday and added an experimental circle with apparently abstract figures that produced a "completely immobile image of a little, perfectly regular horse" when rotated in front of a mirror. After several attempts and many difficulties Plateau managed to animate the figures between the slits in a disc when he constructed the first effective model of the phénakisticope in November or December 1832 . Plateau published his then unnamed invention in a January 20, 1833 letter to ''Correspondance Mathématique et Physique''.
Simon Stampfer Simon Ritter von Stampfer (26 October 1792 (according to other sources 1790)), in Windisch-Mattrai, Archbishopric of Salzburg today called Matrei in Osttirol, Tyrol – 10 November 1864 in Vienna) was an Austrian mathematician, surveyor and ...
claimed to have independently and almost simultaneously invented his very similar ''Stroboscopischen Scheiben oder optischen Zauberscheiben'' (stroboscopic discs or optical magic discs) soon after he read about Faraday's findings in December 1832. Stampfer also mentioned several possible variations of his stroboscopic invention, including a cylinder (similar to the later
zoetrope A zoetrope is one of several pre-film animation devices that produce the illusion of motion by displaying a sequence of drawings or photographs showing progressive phases of that motion. It was basically a cylindrical variation of the phénak ...
) as well as a long, looped strip of paper or canvas stretched around two parallel rollers (somewhat similar to film) and a theater-like frame (much like the later
praxinoscope The praxinoscope was an animation device, the successor to the zoetrope. It was invented in France in 1877 by Charles-Émile Reynaud. Like the zoetrope, it used a strip of pictures placed around the inner surface of a spinning cylinder. The p ...
). In January 1834, William George Horner also suggested a cylindrical variation of Plateau's phénakisticope, but he did not manage to publish a working version. William Ensign Lincoln invented the definitive zoetrope with exchangeable animation strips in 1865 and had it published by Milton Bradley and Co. in December 1866.Herbert, Stephen. (n.d.
''From Daedaleum to Zoetrope'', Part 1.
Retrieved 2014-05-31.


Other theories for motion perception in film

In his 1833 patent and his explanatory pamphlet for his stroboscopic discs, Simon Stampfer emphasized the importance of the interruptions of the beams of light reflected by the drawings, while a mechanism would transport the images past the eyes at an appropriate speed. The pictures had to be constructed according to certain laws of physics and mathematics, including the systematic division of a movement into separate moments. He described the idea of persistence of vision only as the effect that made the interruptions go unnoticed. The idea that the motion effects in so-called "optical toys", like the phénakisticope and the zoetrope, may be caused by images lingering on the retina was questioned in an 1868 article by William Benjamin Carpenter. He suggested that the illusion was "rather a ''mental'' than a ''retinal'' phenomenon". Early theories of persistence of vision were centered on the retina, while later theories preferred or added ideas about cognitive (brain centered) elements of
motion perception Motion perception is the process of inferring the speed and direction of elements in a scene based on visual, vestibular and proprioceptive inputs. Although this process appears straightforward to most observers, it has proven to be a difficult ...
. Many psychological concepts of the basic principle of animation suggested that the blanks in between the images were filled in by the mind.
Max Wertheimer Max Wertheimer (April 15, 1880 – October 12, 1943) was an Austro-Hungarian psychologist who was one of the three founders of Gestalt psychology, along with Kurt Koffka and Wolfgang Köhler. He is known for his book, ''Productive Thinking'', an ...
proved in 1912 that test subjects did not see anything in between the two different positions in which a figure was projected by a
tachistocope A tachistoscope is a device that displays an image for a specific amount of time. It can be used to increase recognition speed, to show something too fast to be consciously recognized, or to test which elements of an image are memorable. Proje ...
at the speed that was ideal for the illusion that it was only one figure moving from one position to the next. He used the Greek letter φ (phi) to designate illusions of motion. At higher speeds, when test subjects believed to see both positions more or less simultaneously, a moving objectless phenomenon was seen between and around the projected figures. Wertheimer supposed this "pure
phi phenomenon The term phi phenomenon is used in a narrow sense for an apparent motion that is observed if two nearby optical stimuli are presented in alternation with a relatively high frequency. In contrast to beta movement, seen at lower frequencies, the s ...
" was a more direct sensory experience of motion. The ideal animation illusion of motion across the interval between the figures was later called "
beta movement The term Beta movement is used for the optical illusion of apparent motion in which the very short projection of one figure and a subsequent very short projection of a more or less similar figure in a different location are experienced as one fi ...
". A visual form of memory known as
iconic memory Iconic memory is the visual sensory memory register pertaining to the visual domain and a fast-decaying store of visual information. It is a component of the visual memory system which also includes visual short-term memory (VSTM) and long-term mem ...
has been described as the cause of persistence of vision. Some scientists nowadays consider the entire theory of iconic memory a myth. When contrasting the theory of persistence of vision with that of phi phenomena, an understanding emerges that the eye ''is not a
camera A camera is an optical instrument that can capture an image. Most cameras can capture 2D images, with some more advanced models being able to capture 3D images. At a basic level, most cameras consist of sealed boxes (the camera body), with ...
'' and does not see in frames per second. In other words, vision is not as simple as light registering on a medium since the brain has to make sense of the visual data the eye provides and construct a coherent picture of reality. Although
psychologist A psychologist is a professional who practices psychology and studies mental states, perceptual Perception () is the organization, identification, and interpretation of sensory information in order to represent and understand the pre ...
s and
physiologist Physiology (; ) is the scientific study of functions and mechanisms in a living system. As a sub-discipline of biology, physiology focuses on how organisms, organ systems, individual organs, cells, and biomolecules carry out the chemica ...
s have rejected the relevance of the theory of retinal persistence film viewership, film academics and theorists generally have not, and it persists in citations in many classic and modern film-theory texts.Metz, Christian (1991) ''Film Language: A Semiotics of The Cinema'', trans. Michael Taylor. Chicago: University of Chicago Press. Joseph and Barbara Anderson argue that the phi phenomena privileges a more constructionist approach to the cinema (
David Bordwell David Jay Bordwell (; born July 23, 1947) is an American film theorist and film historian. Since receiving his PhD from the University of Iowa in 1974, he has written more than fifteen volumes on the subject of cinema including ''Narration in ...
,
Noël Carroll Noël Carroll (born 1947) is an American philosopher considered to be one of the leading figures in contemporary philosophy of art. Although Carroll is best known for his work in the philosophy of film (he is a proponent of cognitive film theory ...
, Kirstin Thompson) whereas the persistence of vision privileges a realist approach (
André Bazin André Bazin (; 18 April 1918 – 11 November 1958) was a renowned and influential French film critic and film theorist. Bazin started to write about film in 1943 and was a co-founder of the renowned film magazine ''Cahiers du cinéma'' in 1951, ...
, Christian Metz, Jean-Louis Baudry).


See also

* Afterimage *
Beta movement The term Beta movement is used for the optical illusion of apparent motion in which the very short projection of one figure and a subsequent very short projection of a more or less similar figure in a different location are experienced as one fi ...
* Chronostasis *
Flicker fusion threshold The flicker fusion threshold, critical flicker frequency (CFF) or flicker fusion rate, is a concept in the psychophysics of vision. It is defined as the frequency at which an intermittent light stimulus appears to be completely steady to the avera ...
*
Light writing Light writing is an emerging form of stop motion animation wherein still images captured using the technique known as light painting or light drawing are put in sequence thereby creating the optical illusion of movement for the viewer. Techniq ...
, a physical
animation Animation is a method by which still figures are manipulated to appear as moving images. In traditional animation, images are drawn or painted by hand on transparent celluloid sheets to be photographed and exhibited on film. Today, most ani ...
technique that has the ''appearance'' of persistence of vision. *
Motion perception Motion perception is the process of inferring the speed and direction of elements in a scene based on visual, vestibular and proprioceptive inputs. Although this process appears straightforward to most observers, it has proven to be a difficult ...
*
Phi phenomenon The term phi phenomenon is used in a narrow sense for an apparent motion that is observed if two nearby optical stimuli are presented in alternation with a relatively high frequency. In contrast to beta movement, seen at lower frequencies, the s ...
*
The Persistence of Vision (short story) "The Persistence of Vision" is a short story by American writer John Varley. It was included in the anthology of the same name and in '' The John Varley Reader''. Plot summary A hitchhiker discovers the town of Keller, a commune whose adult inha ...
* Persistence of Vision (film)


References


External links

*
Persistence of Vision


– commentary on whether the concept is really a myth. * ** *
I get it, I know I'm inferior
November 9, 2006,
Pharyngula
' – comments *Burns, Paul
The History of the Discovery of Cinematography
An Illustrated Chronology
Video of a 2D POV display integrated into a bicycle wheel

Build a SpokePOV: LED Bike Wheel Images


– a project designed for beginners to learn soldering, electronics assembly, and programming microcontrollers

– Visual Perception Lecture 8, The Moving Image.
Newsreel film of persistence of vision
– 1936 Newsreel film explaining how persistence of vision was thought to work.
Physics Stack Exchange on Persistence of Vision
– Physics discussion of persistence of vision.
TestUFO Persistence of Vision
Animation demonstrating persistence of vision {{DEFAULTSORT:Persistence Of Vision Visual perception Animation techniques