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In photography and cinematography, a telephoto lens is a lens where the focal length is significantly longer than the focal length of a normal lens. For a 35 mm camera with a 36 mm by 24 mm format, the normal lens is 50 mm and a lens of focal length 70 mm or more is considered telephoto. On the 6 x 6 cm format (on 120 film) the normal lens is 80 mm, focal length above 100 mm are considered telephoto.
In addition to making objects appear closer than they are, the resulting image will also have a certain degree of perspective distortion.
Many telephoto lenses contain a telephoto group, that would allow the lens to be physically shorter than its focal length. Compare with the opposite effect used in retrofocus lenses, which have greater clearance from the rear element to the film plane than their focal length would permit with a conventional optical design.
See angle of view for an example of an image taken by a telephoto lens.
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