- Ratio of focal-length to diameter
- Military: F/d (of reflector type antennas)
Универсальный русско-английский словарь. Академик.ру. 2011.
Ratio of focal-length to diameter
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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
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
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-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
optics — /op tiks/, n. (used with a sing. v.) the branch of physical science that deals with the properties and phenomena of both visible and invisible light and with vision. [1605 15; < ML optica < Gk optiká, n. use of neut. pl. of OPTIKÓS; see OPTIC,… … Universalium
Optical telescope — Eight Inch refracting telescope (Chabot Space and Science Center) An optical telescope is a telescope which is used to gather and focus light mainly from the visible part of the electromagnetic spectrum for directly viewing a magnified image for… … Wikipedia
photoreception — photoreceptive, adj. /foh toh ri sep sheuhn/, n. the physiological perception of light. [1905 10; PHOTO + RECEPTION] * * * Biological responses to stimulation by light, most often referring to the mechanism of vision. In one celled organisms such … Universalium
relative aperture — Optics. the ratio of the diameter of a lens, esp. a camera lens, to the focal length; the reciprocal of the f number or focal ratio of the lens. * * * ▪ optics the measure of the light gathering power of an optical system. It is expressed… … Universalium
Aperture — For other uses, see Aperture (disambiguation). f stops demonstrated on a lens … Wikipedia
f-stop — F/A/V the ratio of focal length to the effective diameter of a lens; also called f number, it represents how much light is able to pass through the lens. TV Numbers corresponding to variable size of a camera s iris opening, and thus the amount of … Audio and video glossary
Depth of field — The area within the depth of field appears sharp, while the areas in front of and beyond the depth of field appear blurry … Wikipedia
