Prime lens

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Compact 85mm Canon prime lens with a maximum aperture of f/1.8
This Nikon 35mm wide-angle lens is a small, light-weight and "fast" prime lens with a maximum aperture of f/2

In film and photography, a prime lens is either a photographic lens whose focal length is fixed, as opposed to a zoom lens, or it is the primary lens in a combination lens system.

Confusion can sometimes result due to the two meanings of the term if the context does not make the interpretation clear. Alternative terms primary and fixed focal length or FFL are sometimes used to avoid ambiguity.


[edit] As alternative to zoom

The term prime has come to be used as the opposite of zoom; that is, a prime lens is a fixed-focal-length lens, while a zoom lens has a variable focal length.[1][2][3]

A prime lens of a given focal length is less versatile than a zoom whose range includes that focal length, but is often of superior optical quality, lighter weight, smaller bulk and lower cost. This is because prime lens designs are simpler (fewer moving parts), and can be optimized for one particular focal length, whereas zoom lenses must function at a variety of focal lengths. Also since they sport a less complicated lens formula, these lenses won't suffer problems related to chromatic aberration as much as a zoom lens (lenses sporting from 7x and above are very prone to this phenomenon)[citation needed].

Prime lenses usually have a larger maximum aperture (smaller f-number) than zoom lenses. This allows photography in lower light (with the same shutter speed) as well as achieving a shallower depth of field.

In 35 mm photography, a "normal" prime commonly refers to a prime lens with 50 mm focal length, though that is somewhat longer than the film format diagonal of 43.3 mm, which is typically taken to define a normal focal length. Small sensor digital cameras will require shorter focal lengths (in the ratio of their crop factor) to have the same angle of view.

[edit] Traditional meaning as primary lens

An alternate and apparently somewhat older meaning of the term prime lens is the main lens in a combination lens system.[4] When the camera lens is used with some other optical device, such as a close-up lens or teleconverter, the camera lens itself is properly called the prime lens. Prime is here used in the sense of primary, chief, original, first in order, etc.

Lens manufacturers such as ARRI Media[5], ISCO Precision Optics[6], Schneider[7], Carl Zeiss AG[8], Canon[9] and others still make variable focal length cine and video lenses regularly catalogued as variable primes. A variable prime is sometimes distinguished from a "true zoom" in that the latter maintains focus as the focal length is varied.

This use of the term "prime lens" is an example of a retronym. Early in photography only primary camera lenses were available, and were merely called "lenses" or "objectives". Later, "auxiliary" lenses were available, which usually fit in front of the front element of the primary, or "prime" lens.

[edit] References

  1. ^ Lenny Lipton (1975). The Super 8 Book. Simon and Schuster. pp. 61. ISBN 0879320915. 
  2. ^ A. Arthur Englander and Paul Petzold (1976). Filming for Television. Hastings House. 
  3. ^ Gerald Millerson (1993). Effective TV Production. Focal Press. ISBN 024051324X. 
  4. ^ The British Journal of Photography (v.115 ed.). Liverpool Photographic Society. 1967. 
  5. ^ "ARRI Variable Prime Lenses". ARRI Media. Retrieved on 2007-11-19. 
  6. ^ "Variable Prime System for 35 mm Film". ISCO Precision Optics. Retrieved on 2007-11-19. 
  7. ^ "Variable Prime". Schneider Optics. Retrieved on 2007-11-19. 
  8. ^ "1998 Scientific & Technical Awards Winners". Academy of Motion Picture Arts and Sciences. Retrieved on 2007-11-19. 
  9. ^ "AMPAS Award". Academy of Motion Picture Arts and Sciences. Retrieved on 2007-11-19. 

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