Editing Persistence of vision (section)

==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===Historical references to afterimages and motion blur===
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]] ({{circa|15 October 99 BC|55 BC}}), although he only mentions something similar in connection with images seen in a dream.<ref>Herbert, S. (2000). A history of pre-cinema. London. Routledge. p 121</ref>

Around 165 AD [[Ptolemy]] described in his book ''[[Optics (Ptolemy)|Optics]]'' 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."<ref name=smith>{{cite book|url=https://books.google.com/books?id=ASILAAAAIAAJ&q=ptolemy+potter's+wheel&pg=PA43|title=Ptolemy and the Foundations of Ancient Mathematical Optics: A Source Based Guided Study|first=A. Mark|last=Smith|date=29 October 1999|publisher=American Philosophical Society|access-date=29 October 2017|via=Google Books|isbn=9780871698933}}</ref><ref>{{cite journal|jstor=3231951|title=Ptolemy's Theory of Visual Perception: An English Translation of the "Optics" with Introduction and Commentary|first=A. Mark|last=Smith|date=29 October 1996|journal=Transactions of the American Philosophical Society|volume=86|issue=2|pages=iii–300|doi=10.2307/3231951}}</ref>

[[Porphyry (philosopher)|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."<ref>{{cite book|url=https://books.google.com/books?id=c6QKDgAAQBAJ&q=ptolemy+spinning+top&pg=PA137|title=Porphyry's Commentary on Ptolemy's Harmonics: A Greek Text and Annotated Translation|date=15 September 2015|publisher=Cambridge University Press|access-date=29 October 2017|via=Google Books|isbn=9781316239681}}</ref>

In the 11th century [[Ibn al-Haytham]], 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".<ref>{{cite book|url=https://books.google.com/books?id=3x0LAAAAIAAJ&q=ptolemy+optics+color+rotating+wheel&pg=PA444|title=Alhacen's Theory of Visual Perception: A Critical Edition, with English Translation and Commentary, of the First Three Books of Alhacen's De Aspectibus, the Medieval Latin Version of Ibn Al-Haytham's Kitab Al-Manazir|last1=Alhazen|first2=A. Mark|last2=Smith|date=29 October 2017|publisher=American Philosophical Society|access-date=29 October 2017|via=Google Books|isbn=9780871699145}}</ref>

[[Leonardo da Vinci]] 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."<ref>{{Cite book | url=https://books.google.com/books?id=xeaqDsktcc8C&q=%22every%20body%20that%20moves%20rapidly%20seems%20to%22&pg=PA132 | title=Notebooks| isbn=9780191608896| author=Leonardo da Vinci| date=2008-04-17| publisher=OUP Oxford}}</ref>

In his 1704 book ''[[Opticks]]'', [[Isaac Newton]] (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."<ref>{{cite web|url=https://books.google.com/books?id=GnAFAAAAQAAJ&q=newton+Theory+about+Light+and+Colors&pg=PA123|title=Opticks:: Or, A Treatise of the Reflections, Refractions, Inflections and Colours of Light|first=Sir Isaac|last=Newton|date=29 October 2017|publisher=William Innys at the West-End of St. Paul's.|access-date=29 October 2017|via=Google Books}}</ref>

In 1768 [[Patrick d'Arcy]] (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,<ref name="d'Arcy1768">{{Cite book |url=https://books.google.com/books?id=cL5eAAAAcAAJ&pg=RA1-PA439 |title=Histoire De L'Academie Royale Des Sciences. Année ... Avec les Memoires de Mathematique & de Physique, pour la même Année. Tirés des Registres de cette Academie |date=1768 |publisher=Boudot, Jean |language=fr}}</ref> but no results seem to have been published.

===1820–1866: Revolving wheel===
[[File:1820-12-01 j.m. - an optical deception - wood-cut.jpg|thumb|Wood-cut illustration of ''An Optical Deception'' (1821)]]
[[File:1824 roget.jpg|thumb|Illustration plate for Peter Mark Roget's ''Explanation of an Optical Deception in the Appearance of the Spokes of a Wheel Seen through Vertical Apertures'' (1825)]]
[[File:Illustrations of Michael Faraday's paper "On a Peculiar Class of Optical Deceptions" (1831).jpg|thumb|Illustrations of Michael Faraday's experiments with rotating wheels with cogs or spokes (1831)]] 
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.<ref>{{cite book|url=https://books.google.com/books?id=npFlCwAAQBAJ&q=%22john+murray%22+wheel+roget&pg=PP31|title=Seeing Motion: A History of Visual Perception in Art and Science|first=Romana Karla|last=Schuler|date=15 January 2016|publisher=Walter de Gruyter GmbH & Co KG|access-date=29 October 2017|via=Google Books|isbn=9783110422993}}</ref> 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".<ref>{{cite book|url=https://archive.org/stream/quarterlyjournal10roya#page/282/mode/2up|title=Account of an optical deception|author=J.M.|date=1820-12-01}}</ref> Four years later [[Peter Mark Roget]] offered an explanation when reading at the [[Royal Society]] 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.<ref>{{cite journal|url=http://rstl.royalsocietypublishing.org/content/115/131.full.pdf+html|title=Explanation of an optical deception in the appearance of the spokes of a wheel when seen through vertical apertures|date=1824-12-09|last=Roget|first=Peter Mark|journal=Philosophical Transactions of the Royal Society of London |volume=115 |pages=131–140 |doi=10.1098/rstl.1825.0007 |s2cid=144913861 }}</ref>

As a university student [[Joseph Plateau]] 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|Peter Mark Roget's]] 1824 article and decided to investigate the phenomenon further. He published his findings in ''Correspondance Mathématique et Physique'' in 1828<ref>{{cite book |url=https://books.google.com/books?id=ezcDAAAAQAAJ&pg=PA393 |title=Correspondance mathématique et physique |publisher=Garnier and Quetelet |location=Brussels |language=fr |page=393 |year=1828 |volume=4}}</ref> and 1830.<ref>{{cite book |url=https://books.google.com/books?id=wDcDAAAAQAAJ&pg=PA121 |title=Correspondance mathématique et physique |publisher=Garnier and Quetelet |location=Brussels |language=fr |page=121 |year=1830 |volume=6}}</ref> 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''.<ref>{{cite book|url=http://orbi.ulg.ac.be/bitstream/2268/501/1/Plateau_phd.pdf|title=Sur quelques propriétés des impressions produites par la lumière sur l'organe de la vue|last=Plateau|first=Joseph|year=1829|language=fr}}</ref> 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]] wrote a paper for the ''Journal of the [[Royal Institution]] 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.<ref>{{cite book|url=https://archive.org/stream/journalofroyalin01roya#page/204/mode/2up|title=On a peculiar Class of Optical Deceptions|last=Faraday|first=Michael|date=February 1831}}</ref> 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.<ref>{{Cite book|last=Royal Institution of Great Britain|url=http://archive.org/details/journalofroyalin01roya|title=Journal of the Royal Institution of Great Britain|date=1831|publisher=London : Royal Institution of Great Britain|others=London Natural History Museum Library}}</ref>

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.<ref>{{cite book|title=letter to Faraday|last=Plateau|first=Joseph|date=1833-03-08|url=https://books.google.com/books?id=9lknVoNGj30C&q=%22Annales%20de%20physique%20et%20de%20chimie%22%20faraday%20plateau&pg=PA71|isbn=9780863412493}}</ref><ref>{{cite book|title=letter to Faraday|last=Plateau|first=Joseph|date=1832-07-24|url=https://books.google.com/books?id=9lknVoNGj30C&q=%22Annales%20de%20physique%20et%20de%20chimie%22%20faraday%20plateau&pg=PA107|isbn=9780863412493}}</ref> 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 '''[[phenakistiscope|phénakisticope]]''' in November or December 1832 . Plateau published his then unnamed invention in a January 20, 1833 letter to ''Correspondance Mathématique et Physique''.<ref>{{cite book |url=https://books.google.com/books?id=RxNbAAAAYAAJ&pg=PA365 |title=Correspondance mathématique et physique |publisher=Garnier and Quetelet |location=Brussels |language=fr |page=365 |year=1832 |volume=7}}</ref>

[[Simon Stampfer]] 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.<ref name=Stampfer1833>{{cite book |url=https://books.google.com/books?id=xUk0AQAAMAAJ&pg=PA2 |title=Die stroboscopischen Scheiben; oder, Optischen Zauberscheiben: Deren Theorie und wissenschaftliche anwendung, erklärt von dem Erfinder|trans-title=The stroboscopic discs; or optical magic discs: Its theory and scientific application, explained by the inventor |first=Simon |last=Stampfer |language=de |publisher=Trentsensky and Vieweg |location=Vienna and Leipzig |page=2 |year=1833}}</ref>

Stampfer also mentioned several possible variations of his [[stroboscope|stroboscopic]] invention, including a cylinder (similar to the later '''[[zoetrope]]''') 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]]).<ref name=Stampfer1833/> 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.<ref name="horner-1">{{cite book |title=The London and Edinburgh Philosophical Magazine and Journal of Science |year=1834 |page=36 |url=https://books.google.com/books?id=XmrkAAAAMAAJ&q=On+the+Properties+of+the+Daedaleum,+A+New+Instrument+of+Optical+Illusion&pg=PA36}}</ref> William Ensign Lincoln invented the definitive zoetrope with exchangeable animation strips in 1865 and had it published by [[Milton Bradley Company|Milton Bradley and Co.]] in December 1866.<ref name="Herbert1">Herbert, Stephen. (n.d.) {{usurped|1=[https://web.archive.org/web/20140505163417/http://www.stephenherbert.co.uk/wheelZOETROPEpart1.htm ''From Daedaleum to Zoetrope'', Part 1.]}} Retrieved 2014-05-31.</ref>