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In photography, angle of view (also referred to as field of view) is the extent of a given scene that is imaged onto the film or, in digital photography, the image sensor of a camera; that is, there is generally much more to a scene visible to humans than shows up in photos, and lenses of different focal lengths facilitate the recordation of different portions of that total scene. The angle of view of a camera is a function three parameters: It follows that for lenses producing rectilinear images, the aperture dimensions or image sensor size completely define the angle of view for any given lens focal length. These are usually calculated three ways: For a lens producing a rectilinear image, the angle of view (α) can be calculated from the chosen dimension (d), and effective focal length (ƒ) thus: If the chosen dimension is to be the diagonal, then it can be calculated from the horizontal and vertical dimensions of the aperture or image sensor through the use of the Pythagorean Theorem: where h is the horizontal dimension of the image aperture or photosensor and v is its vertical dimension. For example, the diagonal measurement of the image aperture for a full-frame 35 mm camera is: Note that the effective focal length can simply be set equal to the stated focal length of the lens (F), except in macro photography where the magnification factor (m) must be taken into account: Lenses are often referred to by terms that express their angle of view: Zoom lenses are a special case wherein the focal length, and hence angle of view, of the lens can be altered mechanically without removing the lens from the camera. Longer lenses magnify the subject more, compressing distance and (when focused on the foreground) blurring the background because of their shallower depth of field. Wider lenses tend to magnify distance between objects while allowing greater depth of field. One result of using a wide angle lens in proximity to the subject is an apparent perspective distortion: parallel lines may appear to converge and with a fisheye lens, straight edges will appear to bend. Because different lenses generally require a different camera–subject distance to preserve the size of a subject, changing the angle of view can indirectly distort perspective, changing the apparent relative size of the subject and foreground. Note that the angle of view of a given lens is frequently, and incorrectly, referred to as the angle of coverage; a term which describes the properties of the image projected by the lens onto the focal plane. This confusion is not normally an issue with 135 film systems, such as single lens reflex cameras, as the relationship between the lens itself and the film size is almost always fixed. With a view camera, however, the photographer is permitted complete control over the lens–film relationship as well as the lens–subject relationship and thus the two factors come into play. A circular fisheye lens, as opposed to a full-frame fisheye, is an example of a lens where the angle of coverage has been narrowed relative to the other lenses in that system. In many cases the angle of view of the circular fisheye will be almost exactly the same as the nearest full-frame fisheye; however, the image projected onto the film is rendered circular because the diameter of the image projected is narrower than that needed to cover the widest portion of the film.
Common lens angles of view This table shows the diagonal, horizontal, and vertical angles of view, in degrees, for lenses producing rectilinear images used with 24×36 mm format (that is, 135 film or full-frame 35mm digital) Notes | ||||||||
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