L'opacité est l'inverse de la transparence. Qui s'oppose au passage de la lumière.
En optique, l'opacité est l'inverse de la réflectance ou de la transmittance :
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Pour un filtre, l'opacité est le rapport entre le flux incident et le flux transmis.
Pour les négatifs photographiques, la plage de variation de l'opacité étant énorme, on préfère utiliser la notion de densité optique.
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opaque — [ ɔpak ] adj. • XIVe; lat. opacus « ombragé, touffu » 1 ♦ Qui s oppose au passage de la lumière. Verre opaque. « Le brouillard qui rendait pesante, opaque et nauséabonde la nuit » ( Maupassant). Collant opaque. ♢ OPAQUE À... : qui s oppose au… … Encyclopédie Universelle
opaque — [ō pāk′] adj. [ME opake < L opacus, shady] 1. not letting light pass through; not transparent or translucent 2. not reflecting light; not shining or lustrous; dull or dark 3. not allowing electricity, heat, etc. to pass through 4. hard to… … English World dictionary
opaque — UK US /əʊˈpeɪk/ adjective ► difficult to understand or know about, especially because things have been intentionally kept secret or made complicated: »Governments have been able to maintain opaque and discriminatory procurement practices.… … Financial and business terms
opaque — OPAQUE. adj. de tout genre. Terme dogmatique. Qui n est pas transparent. Corps opaque. cela est d une matiere opaque … Dictionnaire de l'Académie française
Opaque — O*paque , a. [F., fr. L. opacus. Cf. {Opacous}.] [1913 Webster] 1. Impervious to the rays of light; not transparent; as, an opaque substance. [1913 Webster] 2. Obscure; not clear; unintelligible. [Colloq.] [1913 Webster] … The Collaborative International Dictionary of English
Opaque — O*paque , n. That which is opaque; opacity. Young. [1913 Webster] … The Collaborative International Dictionary of English
opaque — (adj.) early 15c., opake, from L. opacus shaded, shady, dark, of unknown origin. Spelling influenced after c.1650 by Fr. opaque (c.1500), from the Latin. Figurative use from 1761. Related: Opaquely; opaqueness … Etymology dictionary
opaque — [adj1] clouded, muddy blurred, cloudy, dark, darkened, dim, dirty, dull, dusky, filmy, foggy, frosty, fuliginous, gloomy, hazy, impenetrable, lusterless, misty, muddied, murky, nontranslucent, nontransparent, nubilous, obfuscated, shady, smoky,… … New thesaurus
opaque — ► ADJECTIVE (opaquer, opaquest) 1) not able to be seen through; not transparent. 2) difficult or impossible to understand. ► NOUN Photography ▪ a substance for producing opaque areas on negatives. DERIVATIVES opaquely adverb … English terms dictionary
opaque — I adjective addlebrained, addleheaded, addlepated, ambiguous, asinine, benighted, bewildering, birdbrained, blind, blockish, boeotian, brainless, cloddish, clouded, cloudy, concealed, confused, confusing, cryptic, dark, dense, difficult,… … Law dictionary
opaque — adj. 1 not clear enough to see through VERBS ▪ be, look ▪ become ▪ As the lens becomes more opaque, the patient notices a falling off in vision. ADVERB ▪ com … Collocations dictionary
