Zoom lens

A zoom lens is a mechanical assembly of lenses whose focal length can be changed, as opposed to a prime lens, which has a fixed focal length. They are commonly used with still and video cameras, some binoculars and telescopes, and other optical instruments.

History

Early forms of zoom lenses were used in optical telescopes to provide continuous variation of the magnification of the image, and this was first reported in the proceedings of the Royal Society in 1834. Early patents for telephoto lenses also included moveable lens elements which could be adjusted to change the overall focal length of the lens. Lenses such as these are now called varifocal lenses, in that as the focal length is changed, the position of the focal plane also moves, requiring readjustment of the focussing of the lens after each change.

Related Topics:
Optical telescope - Magnification - Royal Society - 1834 - Patent

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The first real zoom lens, which retained near-sharp focus while the effective focal length of the lens assembly was changed, was patented in 1902 by Clile. C. Allen ({{US patent|696788}}). The first industrial production was the Bell and Howell Cooke "Varo" 40-120mm Lens for 35mm movie cameras introduced in 1932. The Kilfitt 36-82mm/2.8 Zoomar introduced in 1959 was the first zoom lens in regular production for still 35mm photography.

Related Topics:
1902 - Bell and Howell - 1932 - 1959 - 35mm

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Since then, advances in optical design, particularly the use of computers for optical ray tracing, has made the design and construction of zoom lenses much easier, and they are now used widely in professional and amateur photography.

Related Topics:
Computer - Ray tracing

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