exposure

Definition: (1) Process of allowing light to reach light-sensitive material to create latent image: by either (a) opening shutter to expose film or (b) illuminating dark subject with flash of light or energy or (c) both. (2) Amount of light energy that reaches film: it is given by H = Et where E is illuminance and t is time in seconds. * Note: While in theory, any product of E and t that gives the same H gives same exposure, in practice the effect of H on light-sensitive materials will be the same only over small range of E or t. (3) Total radiant energy incident on a surface. * Also known as radiant exposure.
The value of exposure, worth of everything
Exposure is like shopping for expensive things: you're having always to ask 'how much?'. In photography -- whether classical or digital -- we rely on exposure meters to work out how much exposure to give the film. The basic idea is this: the correct exposure is the one that gives you the results you want for the processes you use. This means, assuming that you always want the best image quality, that there's usually only one correct exposure. Forget anything you read about exposure latitude: just work your exposures as accurately as you can.

Related Terms: reciprocity failure

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