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 — 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 — /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 of a lens to its diameter; a measure of the light gathering ability of the lens …   Wiktionary

  • F-number — Индекс диафрагмы (отношение диаметра отверстия диафрагмы к фокусному расстоянию объектива) …   Краткий толковый словарь по полиграфии

  • F number (chemistry) — F number is a number used in chemistry of polycyclic aromatic hydrocarbons (PAHs) as a descriptor of their molecular size. It was proposed by Hurtubise.From a PAH it can be calculated using formula: F = B2 + C12 R / 2, where B2 is a number of… …   Wikipedia

  • F (disambiguation) — F is the sixth letter of the Latin alphabet. F may also refer to:cience*Fahrenheit *Farad, a unit for electric capacitance *Faraday constant *Fluorine *Focal length **f number, the focal length divided by the aperture diameter *Force *FrequencyAs …   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

  • f-system — f sys·tem (ĕfʹsĭs təm) n. A method of indicating the relative aperture of a camera lens based on the f number. * * * …   Universalium

  • F scale — The terms F scale and F number may refer to several things:*The F scale is a personality test that attempts to quantify authoritarian tendencies. *The Fujita scale, sometimes abbreviated F scale , rates a tornado s intensity by its impact on… …   Wikipedia

  • f/ — Photog. See f number. Also, f/, f:. * * * …   Universalium

Share the article and excerpts

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