focal ratio
noun Date: 1926 f-number

New Collegiate Dictionary. 2001.

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  • focal ratio — noun the ratio of the focal length to the diameter of a (camera) lens system • Syn: ↑f number, ↑stop number, ↑speed • Hypernyms: ↑ratio * * * noun : f number …   Useful english dictionary

  • focal ratio — Optics., Photog. f number. [1925 30] * * * …   Universalium

  • Focal length — The focal length of an optical system is a measure of how strongly it converges (focuses) or diverges (diffuses) light. A system with a shorter focal length has greater optical power than one with a long focal length. Thin lens approximation For… …   Wikipedia

  • Focal plane array testing — (under development sep 15)Focal Plane Array testing (FPA testing) is the test engineering process of validation and verification (V V) of operation of focal plane array imaging devices, device under test (DUT), at various levels of the… …   Wikipedia

  • Matthiessen's ratio — For the electron mobility rule, see Matthiessen s rule. In optics, Matthiessen s ratio is the ratio between the distance from the centre of the lens to the objective, versus the lens radius[1]. This is of particular importance in fish, where the… …   Wikipedia

  • F-ratio (disambiguation) — F ratio or f ratio may refer to:* f number, f ratio, or focal ratio, the ratio of the focal length of an optical system to the diameter of its entrance pupil; * f ratio, in oceanography, which relates recycled and total primary production in the… …   Wikipedia

  • 35 mm equivalent focal length — In photography, the 35 mm equivalent focal length is a measure that indicates the angle of view of a particular combination of a camera lens and film or sensor size. The term originates from the time when the vast majority of photography was done …   Wikipedia

  • f ratio —    or f number or f stop (f/ or f)    a measure of the light gathering power of the lenses in cameras and telescopes.    The f ratio, for example f/4 or f4, is the aperture of the lens (the effective diameter of the lens, which may be reduced or… …   Dictionary of units of measurement

  • zoom ratio — TV Range of a lens focal length, from most zoomed in field of view to most zoomed out. Expressed as ratio: 6:1, for example, implies that the same lens from the same distance can make the same image appear six times closer. [See focal length,… …   Audio and video glossary

  • F-number — In optics, the f number (sometimes called focal ratio, f ratio, or relative aperture [Smith, Warren Modern Lens Design 2005 McGraw Hill] ) of an optical system expresses the diameter of the entrance pupil in terms of the focal length of the lens; …   Wikipedia

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