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| {{two other uses||the same phenomenon in photography|Angle of view}}
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| [[File:Cascading Milky Way.jpg|thumb|450px|A 360-degree [[panorama]] of the [[Milky Way]] at the [[Very Large Telescope]]. Such a panorama shows the entire '''field of view''' (FOV) in a single image. An observer would perceive the Milky Way like an arc of stars spanning horizon to horizon – with the entire FOV mapped on a single image this arc appears as two streams of stars seemingly cascading down like waterfalls.<ref>{{cite news|title=Cascading Milky Way|url=http://www.eso.org/public/images/potw1224a/|accessdate=11 June 2012|newspaper=ESO Picture of the Week}}</ref>]]
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| The '''field of view''' (also '''field of vision''', abbreviated '''FOV''' or '''instantaneous field of view''', abbreviated '''IFOV''') is the extent of the observable world that is [[visual perception|seen]] at any given moment. In case of [[optical instrument]]s or sensors it is a [[solid angle]] through which a detector is sensitive to [[electromagnetic radiation]].
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| == Humans and animals ==
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| [[Image:Angle of view.svg|right|thumb|'''Angle of view''' can be measured horizontally, vertically, or diagonally.]]
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| Different animals have different fields of view, depending on the placement of the eyes. [[Human eye#Field of view|Humans have an almost 180-degree forward-facing horizontal field of view]], while some [[Bird vision|birds]] have a complete or nearly complete 360-degree field of view. In addition, the vertical range of the field of view in humans is typically around 135 degrees.
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| The range of visual abilities is not uniform across a field of view, and varies from animal to animal. For example, [[binocular vision]], which is important for [[depth perception]], covers only 120 degrees (horizontally) of the field of vision in humans {{Citation needed|date=February 2011}}; the remaining peripheral 60 degrees have no binocular vision (because only one [[Human eye|eye]] can see those parts of the field of view). Some birds have a scant 10 or 20 degrees of binocular vision.
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| Similarly, [[color vision]] and the ability to perceive shape and motion vary across the field of view; in humans the former is concentrated in the center of the visual field, while the latter tends to be much stronger in the periphery. This is due to the much higher concentration of color-sensitive [[cone cell]]s in the [[fovea]], the central region of the [[retina]], in comparison to the higher concentration of motion-sensitive [[rod cell]]s in the periphery. Since cone cells require considerably brighter light sources to be activated, the result of this distribution is that peripheral vision is much stronger at night relative to binocular vision.
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| ==Conversions==
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| Many optical instruments, particularly [[binoculars]] or spotting scopes, are advertised with their field of view specified in one of two ways: angular field of view, and linear field of view. Angular field of view is typically specified in degrees, while linear field of view is a ratio of lengths. For example, binoculars with a 5.8 [[degree (angle)|degree (angular)]] field of view might be advertised as having a (linear) field of view of 305 ft per 1000 yd or 102 mm per meter. As long as the FOV is less than about 10 degrees or so, the following approximation formulas allow one to convert between linear and angular field of view. Let <math>A</math> be the angular field of view in degrees. Let <math>L</math> be the linear field of view in feet per 1000 yd. Let <math>M</math> be the linear field of view in millimeters per meter. Then, using the [[small-angle approximation]]:
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| :<math>A \approx {360^{\circ}\over 2 \pi} \cdot {L\over 3000 } \approx 0.0191 \times L </math>
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| :<math>A \approx {360^{\circ}\over 2 \pi} \cdot {M\over 1000 } \approx 0.0573 \times M </math>
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| :<math>L \approx {2 \pi \cdot 3000 \over 360^{\circ}} \cdot A \approx 52.36 \times A </math>
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| :<math>M \approx {2 \pi \cdot 1000 \over 360^{\circ}} \cdot A \approx 17.45 \times A </math>
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| == Machine vision ==
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| In [[machine vision]] the lens [[focal length]] and [[image sensor]] size sets up the fixed relationship between the field of view and the working distance. Field of view is the area of the inspection captured on the camera’s imager. The size of the field of view and the size of the camera’s imager directly affect the image resolution (one determining factor in accuracy). Working distance is the distance between the back of the lens and the target object.
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| == Remote Sensing ==
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| In [[remote sensing]], the [[solid angle]] through which a detector is sensitive to electromagnetic radiation at any one time, is called ''instantaneous field of view'' or IFOV. A measure of the [[spatial resolution]] of a remote sensing imaging system, it is often expressed as a dimensions of visible ground area, for some known sensor [[altitude]].<ref>{{cite web|last=Oxford Reference|title=Quick Reference: instantaneous field of view|url=http://www.oxfordreference.com/view/10.1093/oi/authority.20110803100005771|publisher=Oxford University Press|accessdate=13 December 2013}}</ref><ref>{{cite book|last=Wynne|first=James B. Campbell, Randolph H.|title=Introduction to remote sensing|year=2011|publisher=Guilford Press|location=New York|isbn=160918176X|url=http://books.google.com/books?id=NkLmDjSS8TsC&printsec=frontcover&source=gbs_ge_summary_r&cad=0#v=onepage&q&f=false|edition=5th ed.|page=261}}</ref> Single pixel IFOV is closely related to concept of ''resolved pixel size'', [[ground resolved distance]], [[ground sample distance]] and [[modulation transfer function]].
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| ==Astronomy==
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| In astronomy the field of view is usually expressed as an [[Solid angle|angular area]] viewed by the instrument, in [[square degree]]s, or for higher magnification instruments, in square [[arc-minute]]s. For reference the Wide Field Channel on the [[Advanced Camera for Surveys]] on the [[Hubble Space Telescope]] has a field of view of 10 sq. arc-minutes, and the High Resolution Channel of the same instrument has a field of view of 0.15 sq. arc-minutes. Ground based survey telescopes have much wider fields of view. The photographic plates used by the [[UK Schmidt Telescope]] had a field of view of 30 sq. degrees. The 1.8 m (71 in) [[Pan-STARRS]] telescope, with the most advanced digital camera to date has a field of view of 7 sq. degrees. In the near infra-red WFCAM on [[UKIRT]] has a field of view of 0.2 sq. degrees and the forthcoming [[VISTA (telescope)|VISTA]] telescope will have a field of view of 0.6 sq. degrees. Until recently digital cameras could only cover a small field of view compared to [[photographic plate]]s, although they beat photographic plates in [[quantum efficiency]], linearity and dynamic range, as well as being much easier to process.
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| == Photography ==
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| {{main|Angle of view}}
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| In photography, the field of view is that part of the world that is visible through the camera at a particular position and orientation in space; objects outside the FOV when the picture is taken are not recorded in the photograph. It is most often expressed as the angular size of the view cone, as an [[angle of view]]. For normal lens, field of view can be calculated FOV = 2 arctan(SensorSize/2f), where f is [[Focal Length]].
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| == Video games ==
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| {{main|Field of view in video games}}
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| The field of view in [[video game]]s refers to the part you see of a game world, which is dependent on the scaling method used.<ref>[http://artsygamer.com/fov-in-games/ Feng Zhu School of Design – Field of View in Games]</ref>
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| == See also ==
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| * [[Panorama]]
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| * [[Perimetry]]
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| * [[Peripheral vision]]
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| * [[Visual perception]]
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| * [[Useful field of view]]
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| == References ==
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| {{reflist}}
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| <references/>
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| [[Category:Vision]]
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| [[Category:Ophthalmology]]
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| [[Category:Neurology]]
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| [[Category:Science of photography]]
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