f-number
noun Etymology: focal length Date: circa 1903 1. the ratio of the focal length to the aperture in an optical system 2. a number following the symbol f/ that expresses the effectiveness of the aperture of a camera lens in relation to brightness of image so that the smaller the number the brighter the image and therefore the shorter the exposure required

New Collegiate Dictionary. 2001.

Look at other dictionaries:

  • f-number — (f/#)    A number used to indicate the size and light passing ability of the lens opening on most adjustable cameras. Common f numbers are f/2, f/2.8, f/4, f/5.6,f/8, f/11, f/16, and f/22. The larger the f number, the smaller the lens opening.… …   Forensic science glossary

  • f-number — [ef′num΄bər] n. Photog. a number that represents the relative aperture of a lens, equal to the focal length divided by the effective diameter of the lens aperture: a higher number indicates a smaller opening …   English World dictionary

  • 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

  • f-number — n. Photog. the ratio of the focal length to the effective diameter of a lens (e.g. f5, indicating that the focal length is five times the diameter). Etymology: f (denoting focal length) + NUMBER * * * ˈf number 7 [f number f numbers] noun a… …   Useful english dictionary

  • f-number — /ef num beuhr/, n. Optics, Photog. a number corresponding to the ratio of the focal length to the diameter of a lens system, esp. a camera lens. In f/ 1.4, 1.4 is the f number and signifies that the focal length of the lens is 1.4 times as great… …   Universalium

  • f number — noun the ratio of the focal length to the diameter of a (camera) lens system • Syn: ↑focal ratio, ↑stop number, ↑speed • Hypernyms: ↑ratio * * * f number, Photography. the focal length of a lens divided by its effective diameter. An f/4 lens is… …   Useful english dictionary

  • f-number — WikiV (F Stop also known as f number or f system) The speed or ability of a lens to pass light. It is calculated by dividing the focal length of the lens by its diameter. The f stop also is a factor in more areas of focus in the image known as… …   Audio and video glossary

  • f number — /ˈɛf nʌmbə/ (say ef numbuh) noun the ratio of the focal length of a lens system to its effective diameter, used to number aperture openings in a camera. Also, f stop. {f(ocal length) + number} …   Australian English dictionary

  • f-number — [[t]ˈɛfˌnʌm bər[/t]] n. opt pht a number corresponding to the ratio of the focal length to the diameter of a lens system, esp. a camera lens Symbol: f • Etymology: 1890–95 …   From formal English to slang

  • f number —    see f ratio …   Dictionary of units of measurement

Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”