Planar

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The Planar is a double-Gauss lens with six elements made by Zeiss. It was designed by Paul Rudolph who had already designed Zeiss' first anastigmats. The Planar is also anastigmatic, and named for its flat image plane. Being a Gauss type, the lens is symmetrical; each half comprises one converging element and a diverging cemented pair (the cemented groups are in the centre of the lens, closest to the iris diaphragm). The symmetrical design gives inherently low chromatic aberration; however, it suffers from coma.[1] The first version was an f/4.5 lens.

The strengths of the Planar's construction were further developed after the invention of lens coating because the original construction suffered flare. A variant with seven elements was made for 35mm cameras (Glatzel-variant). The Planar is still a Zeiss product, and was the model for many other lens constructions. Many of the derived lenses are not completely symmetrical. The Carl Zeiss Planar 1:0,7/50 mm is the fastest available photographic lens. This super-fast variant was only used by NASA for espionage tasks and by Stanley Kubrick to film scenes with just candle light. Many fast lenses with focal lengths between 35 and 85 mm are derived from the Planar.




Notes

  1. Greenleaf, Allen R. (1950) Photographic Optics. Macmillan, New York. p85.

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