positive

Definition: Adjective: (1) ~ film, ~ image, ~ working: one in which the tone or colour reproduction is broadly similar to that of the image i.e. light tones are reproduced light, blue colours are blue, etc. * Antonym: negative. (2) ~ lens, ~ element: one which converges an incident beam, to produce a real image. (3) ~ distortion: lens aberration in which the image size increases with distance from the optical axis. * Synonym: pincushion distortion. (4) ~ film curl: one in which the emulsion side is concave. (5) ~ screen: type of screen used to make positive half-tone plates. Reversing the rules While we take it for granted that the way we see is the correct way (bright is bright, surely) photography works at heart the opposite way: essentially all photographic processes are negative-working. In order to get a positive image we (almost) always need to interpose an extra step which is, itself, of course negative-working too. Test: which photographic process is positive working? (Clue: it died an early death.)

Related Terms: reversal

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