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[[Image:Parallax.gif|thumb|300px|right|This animation is an example of parallax. As the viewpoint moves side to side, the objects in the distance appear to move more slowly than the objects close to the camera.]] |
[[Image:Parallax.gif|thumb|300px|right|This animation is an example of parallax. As the viewpoint moves side to side, the objects in the distance appear to move more slowly than the objects close to the camera.]] |
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| − | '''Parallax''' is an apparent displacement or difference of orientation of an object viewed along two different lines of sight, and is measured by the angle or semi-angle of inclination between those two lines.<ref>{{cite dictionary | quote=Mutual inclination of two lines meeting in an angle | encyclopedia=Shorter Oxford English Dictionary | year=1968}}</ref><ref name=oed>{{cite dictionary | encyclopedia=Oxford English Dictionary | year=1989 | edition=Second Edition | title=Parallax | quote=''Astron.'' Apparent displacement, or difference in the apparent position, of an object, caused by actual change (or difference) of position of the point of observation; spec. the angular amount of such displacement or difference of position, being the angle contained between the two straight lines drawn to the object from the two different points of view, and constituting a measure of the distance of the object. | url=http://dictionary.oed.com/cgi/entry/50171114?single=1&query_type=word&queryword=parallax&first=1&max_to_show=10 }}</ref> The term is derived from the Greek παράλλαξις (''parallaxis''), meaning "alteration" |
+ | '''Parallax''' is an apparent displacement or difference of orientation of an object viewed along two different lines of sight, and is measured by the angle or semi-angle of inclination between those two lines.<ref>{{cite dictionary | quote=Mutual inclination of two lines meeting in an angle | encyclopedia=Shorter Oxford English Dictionary | year=1968}}</ref><ref name=oed>{{cite dictionary | encyclopedia=Oxford English Dictionary | year=1989 | edition=Second Edition | title=Parallax | quote=''Astron.'' Apparent displacement, or difference in the apparent position, of an object, caused by actual change (or difference) of position of the point of observation; spec. the angular amount of such displacement or difference of position, being the angle contained between the two straight lines drawn to the object from the two different points of view, and constituting a measure of the distance of the object. | url=http://dictionary.oed.com/cgi/entry/50171114?single=1&query_type=word&queryword=parallax&first=1&max_to_show=10 }}</ref> The term is derived from the Greek παράλλαξις (''parallaxis''), meaning "alteration". |
| − | Nearby objects have a larger parallax than more distant objects when observed from different positions, so parallax can be used to determine distances. |
+ | Nearby objects have a larger parallax than more distant objects when observed from different positions, so parallax can be used to determine distances. |
Parallax also affects optical instruments such as binoculars, [[microscope]]s, and twin-lens reflex cameras which view objects from slightly different angles. Many animals, including humans, have two [[eye]]s with overlapping [[visual perception|visual fields]] to use parallax to gain [[depth perception]]; this process is known as [[stereopsis]]. |
Parallax also affects optical instruments such as binoculars, [[microscope]]s, and twin-lens reflex cameras which view objects from slightly different angles. Many animals, including humans, have two [[eye]]s with overlapping [[visual perception|visual fields]] to use parallax to gain [[depth perception]]; this process is known as [[stereopsis]]. |
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== Visual perception == |
== Visual perception == |
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| − | Because the eyes of humans and other highly evolved animals are in different positions on the head, they present different views simultaneously. This is the basis of [[stereopsis]], the process by which the brain exploits the parallax due to the different views from the eye to gain depth perception and estimate distances to objects.<ref>{{citation | last=Steinman | first=Scott B. | last2=Garzia | first2=Ralph Philip | year=2000 | title=Foundations of Binocular Vision: A Clinical perspective | publisher=McGraw-Hill Professional | isbn=0-8385-2670-5 | pages=2–5}}</ref> |
+ | Because the eyes of humans and other highly evolved animals are in different positions on the head, they present different views simultaneously. This is the basis of [[stereopsis]], the process by which the brain exploits the parallax due to the different views from the eye to gain depth perception and estimate distances to objects.<ref>{{citation | last=Steinman | first=Scott B. | last2=Garzia | first2=Ralph Philip | year=2000 | title=Foundations of Binocular Vision: A Clinical perspective | publisher=McGraw-Hill Professional | isbn=0-8385-2670-5 | pages=2–5}}</ref> |
Animals also use ''motion parallax'', in which the animal (or just the head) moves to gain different viewpoints. For example, [[pigeon]]s (whose eyes do not have overlapping fields of view and thus cannot use stereopsis) bob their heads up and down to see depth.<ref>{{harvnb|Steinman|Garzia|2000|loc=p. 180}}.</ref> |
Animals also use ''motion parallax'', in which the animal (or just the head) moves to gain different viewpoints. For example, [[pigeon]]s (whose eyes do not have overlapping fields of view and thus cannot use stereopsis) bob their heads up and down to see depth.<ref>{{harvnb|Steinman|Garzia|2000|loc=p. 180}}.</ref> |
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| − | ==See also == |
+ | ==See also == |
* [[Binocular disparity|Disparity]] |
* [[Binocular disparity|Disparity]] |
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* [[Binocular vision]] |
* [[Binocular vision]] |
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==References== |
==References== |
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{{reflist}} |
{{reflist}} |
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| + | |||
[[Category:Distance perception]] |
[[Category:Distance perception]] |
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[[Category:Motion perception]] |
[[Category:Motion perception]] |
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A simplified illustration of the parallax of an object against a distant background due to a perspective shift. When viewed from "Viewpoint A", the object appears to be in front of the blue square. When the viewpoint is changed to "Viewpoint B", the object appears to have moved in front of the red square.
This animation is an example of parallax. As the viewpoint moves side to side, the objects in the distance appear to move more slowly than the objects close to the camera.
Parallax is an apparent displacement or difference of orientation of an object viewed along two different lines of sight, and is measured by the angle or semi-angle of inclination between those two lines.[1][2] The term is derived from the Greek παράλλαξις (parallaxis), meaning "alteration".
Nearby objects have a larger parallax than more distant objects when observed from different positions, so parallax can be used to determine distances.
Parallax also affects optical instruments such as binoculars, microscopes, and twin-lens reflex cameras which view objects from slightly different angles. Many animals, including humans, have two eyes with overlapping visual fields to use parallax to gain depth perception; this process is known as stereopsis.
Visual perception
Because the eyes of humans and other highly evolved animals are in different positions on the head, they present different views simultaneously. This is the basis of stereopsis, the process by which the brain exploits the parallax due to the different views from the eye to gain depth perception and estimate distances to objects.[3]
Animals also use motion parallax, in which the animal (or just the head) moves to gain different viewpoints. For example, pigeons (whose eyes do not have overlapping fields of view and thus cannot use stereopsis) bob their heads up and down to see depth.[4]
See also
- Disparity
- Binocular vision
- Depth perception
- Distance perception
- Form and shape perception
- Monocular vision
- Motion perception
References
- ↑ Template:Cite dictionary
- ↑ Template:Cite dictionary
- ↑ Steinman, Scott B.; Garzia, Ralph Philip (2000), Foundations of Binocular Vision: A Clinical perspective, McGraw-Hill Professional, pp. 2–5, ISBN 0-8385-2670-5
- ↑ Steinman & Garzia 2000, p. 180.