Editing Ewald Hering (section)

===Binocular vision===
[[File:Heringvisualdirection.png|thumb|Hering's demonstration of his law of visual direction]]

Hering studied a broad range of subjects in vision, among them his outstanding studies on binocular vision.
<ref>{{cite book | author=Hering, Ewald |title =Die Lehre vom binokularem Sehen | location=Leipzig | year=1868}}</ref><ref>{{cite book |author=Hering, Ewald |title=The theory of binocular vision: Ewald Hering (1868); edited by Bruce Bridgeman and Lawrence Stark; translation and introduction by Bruce Bridgeman; commentary by Lawrence Stark |publisher=Plenum Press |location=New York |year= 1977 |isbn=978-0306310164  }}</ref> He derived, almost simultaneously with Helmholtz, the theoretical shape of the horopter. Despite identical results, Hering's derivation was far more modern and elegant, using recently developed projective geometry. Indeed, Helmholtz himself qualified Hering's approach as "very elegant, comprehensive and complete". Subsequently, Hering empirically estimated the shape of the horopter. Alongside with [[Helmholtz]] and [[Hillebrand]], he noticed that the empirical horopter does not match the theoretical horopter, a phenomenon now named the [[Hering–Hillebrand deviation]].

Hering is also well known for his [[Hering's law of visual direction|Law of Visual Direction]] which describes the perceived egocentric direction of an object from an observer. Unbeknownst to Hering and other visual scientists of the time, a similar law had been proposed by [[Alhazen]] (1021) <ref>{{cite book|last1=Smith|first1=A. Mark|title=Alhacen's theory of visual perception. Volume Two, English Translation.|date=2001|publisher=American Philosophical Society|location=Philadelphia}}</ref> and [[William Charles Wells|Wells]] (1792) <ref>{{cite book|last1=Wells|first1=W. C.|title=An Essay upon Single Vision with Two Eyes: Together with Experiments and Observations on Several Other Subjects in Optics|url=https://archive.org/details/essayuponsinglev00well|date=1792|publisher=Cadell|location=London}}</ref> 
although both their laws were different.