—speedful, adj. —speedfully, adv. —speedfulness, n. —speedingly, adv. —speedingness, n. —speedless, adj.n.1. rapidity in moving, going, traveling, proceeding, or performing; swiftness; celerity: the speed of light; the speed of sound.2. relative rapidity in moving, going, etc.; rate of motion or progress: full speed ahead.3. full, maximum, or optimum rate of motion: The car gets to speed in just nine seconds.4. Auto. a transmission gear ratio.5. Photog.a. Also called film speed. the sensitivity of a film or paper to light, measured by an ASA or DIN index, which assigns low numbers to slow film and higher numbers to faster film.b. Also called shutter speed. the length of time a shutter is opened to expose film.c. the largest opening at which a lens can be used.6. Slang. a stimulating drug, as caffeine, ephedrine, or esp. methamphetamine or amphetamine.7. Informal. a person or thing that is compatible with or typical of one's ability, personality, desires, etc.: My speed is writing postcards on the porch while everyone else is tearing around the tennis court.8. Archaic. success or prosperity.9. at full or top speed,a. at the greatest speed possible: We drove down the highway at full speed.b. to the maximum of one's capabilities; with great rapidity: He worked at full speed.10. up to speed,a. operating at full or optimum speed.b. functioning or producing at an expected, acceptable, or competitive level; up to par: a new firm not yet up to speed.v.t.11. to promote the success of (an affair, undertaking, etc.); further, forward, or expedite.13. to increase the rate of speed of (usually fol. by up): to speed up industrial production.14. to bring to a particular speed, as a machine.15. to cause to move, go, or proceed with speed.16. to expedite the going of: to speed the parting guest.17. Archaic. to cause to succeed or prosper.v.i.18. to move, go, pass, or proceed with speed or rapidity.19. to drive a vehicle at a rate that exceeds the legally established maximum: He was arrested for speeding.20. to increase the rate of speed or progress (usually fol. by up).21. to get on or fare in a specified or particular manner.22. Archaic. to succeed or prosper.[bef. 900; 1965-70 for def. 6; (n.) ME spede good luck, prosperity, rapidity, OE sped; c. D spoed, OHG spot; akin to OE spowan to prosper, succeed; (v.) ME speden to succeed, prosper, go with speed, OE spedan to succeed, prosper; c. OS spodian, OHG spuoten]Syn. 1, 2. fleetness, alacrity, dispatch, expedition; hurry. SPEED, VELOCITY, QUICKNESS, RAPIDITY, CELERITY, HASTE refer to swift or energetic movement or operation. SPEED (originally prosperity or success) may apply to human or nonhuman activity and emphasizes the rate in time at which something travels or operates: the speed of light, of a lens, of an automobile, of thought. VELOCITY, a more learned or technical term, is sometimes interchangeable with SPEED: the velocity of light; it is commonly used to refer to high rates of speed, linear or circular: velocity of a projectile.QUICKNESS, a native word, and RAPIDITY, a synonym of Latin origin, suggest speed of movement or operation on a small or subordinate scale; QUICKNESS applies more to people (quickness of mind, of perception, of bodily movement), RAPIDITY more to things, often in a technical or mechanical context: the rapidity of moving parts; a lens of great rapidity. CELERITY, a somewhat literary synonym of Latin origin, refers usually to human movement or operation and emphasizes expedition, dispatch, or economy in an activity: the celerity of his response.HASTE refers to the energetic activity of human beings under stress; it often suggests lack of opportunity for care or thought: to marry in haste; a report prepared in haste. 11. advance, favor. 13. accelerate. 18. See rush1.Ant. 1. slowness.
* * *in photography, any of those standards that indicate (1) the size of the lens opening, or aperture, (2) the duration of exposure, and (3) the sensitivity of the film to light.The aperture, or lens speed, of a camera is the size of the opening in the lens. Aperture settings provide one means of controlling the amount of light that falls on the film by determining the maximum diameter of the light beam entering the camera body. A standard set of numbers, called f-stops, describe the lens aperture as a ratio of the focal length (see relative aperture).The shutter speed regulates the length of time that the shutter is open during an exposure. Varying the shutter speed controls the film's exposure to light and determines the speed of action that the photograph can “freeze,” or reproduce without blurring the image. Shutter speeds generally range from one second to 1/2,000 of a second.Film speed indicates the sensitivity of a particular emulsion to light. It is usually expressed as an ISO (International Standards Organization) number (formerly called, and identical to, the ASA [American Standards Association; now American National Standards Institute] number), or, in Europe, as a DIN (Deutsche Industrie Norm) number. A film with a speed of 32 ISO/ASA, or 16/10 DIN, for example, would be considered a slow film—i.e., relatively insensitive to light, and most effectively used in bright light—whereas one with a speed of 400 ISO/ASA, or 27/10 DIN, would be considered fast—i.e., relatively sensitive to light and therefore usable in dim light or with a very fast shutter speed.
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