Thefield of view (FOV) is theangular extent of the observable world that isseen at any given moment. In the case ofoptical instruments or sensors, it is asolid angle through which a detector is sensitive toelectromagnetic radiation. It is further relevant inphotography.

In the context of human and primate vision, the term "field of view" is typically only used in the sense of a restriction to what is visible by external apparatus, like when wearing spectacles^[1] orvirtual reality goggles. Note that eye movements are allowed in the definition but do not change the field of view when understood this way.

If the analogy of the eye's retina working as a sensor is drawn upon, the corresponding concept in human (and much of animal vision) is thevisual field.^[2] It is defined as "the number of degrees of visual angle during stable fixation of the eyes".^[3] Note that eye movements are excluded in the visual field's definition.Humans have a slightly over 210-degree forward-facing horizontal arc of their visual field (i.e. without eye movements),^[4][5][6] (with eye movements included it is slightly larger, as you can try for yourself by wiggling a finger on the side), while somebirds have a complete or nearly complete 360-degree visual field. The vertical range of the visual field in humans is around 150 degrees.^[4]

The range of visual abilities is not uniform across the visual field which also varies betweenspecies. For example,binocular vision, which is the basis forstereopsis and is important fordepth perception, covers 114 degrees (horizontally) of the visual field in humans;^[7] the remaining ~50 degrees on each side^[6] ofperipheral vision have no binocular vision (because only one eye can see those parts of the visual field). Some birds have a scant 10 to 20 degrees of binocular vision.

Similarly,color vision and the ability to perceive shape and motion vary across the visual field; in humans color vision and form perception are concentrated in the center of the visual field, while motion perception is only slightly reduced in the periphery and thus has a relative advantage there. The physiological basis for that is the much higher concentration of color-sensitivecone cells and color-sensitiveparvocellularretinal ganglion cells in thefovea – the central region of the retina, together with a largerrepresentation in the visual cortex – in comparison to the higher concentration of color-insensitiverod cells and motion-sensitivemagnocellularretinal ganglion cells in the visual periphery, and smaller cortical representation. Since rod cells require considerably less light to be activated, the result of this distribution is further that peripheral vision is much more sensitive at night relative to foveal vision (sensitivity is highest at around 20 deg eccentricity).^[2]

Many optical instruments, particularlybinoculars 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 5.8degree (angular) field of view might be advertised as having a (linear) field of view of 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${\displaystyle A}$ be the angular field of view in degrees. Let${\displaystyle M}$ be the linear field of view in millimeters per meter. Then, using thesmall-angle approximation:

${\displaystyle A\approx \frac{{360}^{\circ }}{2\pi }\cdot \frac{M}{1000}\approx 0.0573\times M}$

${\displaystyle M\approx \frac{2\pi \cdot 1000}{{360}^{\circ }}\cdot A\approx 17.45\times A}$

Inmachine vision the lensfocal length andimage 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.

Intomography, the field of view is the area of each tomogram. In for examplecomputed tomography, a volume ofvoxels can be created from such tomograms by merging multiple slices along the scan range.

Inremote sensing, thesolid angle through which a detector element (a pixel sensor) is sensitive to electromagnetic radiation at any one time, is calledinstantaneous field of view or IFOV. A measure of thespatial resolution of a remote sensing imaging system, it is often expressed as dimensions of visible ground area, for some known sensoraltitude.^[8][9] Single pixel IFOV is closely related to concept ofground resolved distance,ground sample distance,modulation transfer function, andresolved pixel size.

Inastronomy, the field of view is usually expressed as anangular area viewed by the instrument, insquare degrees, or for higher magnification instruments, in squarearc-minutes. For reference the Wide Field Channel on theAdvanced Camera for Surveys on theHubble 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 theUK 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 onUKIRT has a field of view of 0.2 sq. degrees and theVISTA telescope has a field of view of 0.6 sq. degrees. Until recently digital cameras could only cover a small field of view compared tophotographic plates, although they beat photographic plates inquantum efficiency, linearity and dynamic range, as well as being much easier to process.

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 anangle of view. For a normal lens focused at infinity, the diagonal (or horizontal or vertical) field of view can be calculated as:

${\displaystyle \mathrm{F}\mathrm{O}\mathrm{V}=2\times \arctan \left(\frac{s}{2f}\right)}$

Where:

• ${\displaystyle s}$ is thesensor size (diagonal, width, or height);
• ${\displaystyle f}$ is thefocal length of the lens.

In microscopy, the field of view in high power (usually a 400-foldmagnification when referenced in scientific papers) is called ahigh-power field, and is used as a reference point for various classification schemes.

For an objective with magnification${\displaystyle m}$, the FOV is related to the Field Number (FN) by

${\displaystyle \mathrm{F}\mathrm{O}\mathrm{V}=\frac{\mathrm{F}\mathrm{N}}{m},}$

if other magnifying lenses are used in the system (in addition to the objective), the total${\displaystyle m}$ for the projection is used.

The field of view invideo games refers to the field of view of the camera looking at the game world, which is dependent on the scaling method used.

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• Science of photography

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