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A film's exposure latitude is often defined as the amount by which exposure can be varied without losing detail and hence degrading images. This is an almost meaningless definition that provides widely-quoted misleading measurements. The problem with the definition is that, strictly speaking, films have zero exposure latitude for a given subject and particular aesthetic requirements. Exposure must be exactly what is required to produce the desired result.

Some scenes incorporate much wider ranges of brightness, and hence tolerance of exposure variations, than others. The brightness of a clear sky might typically be four or five stops greater than a foreground. If a camera is directed towards the sun, the range of brightness in a scene increases further and may well exceed the dynamic range of a film (or incidentally a sensor). However if the same scene is photographed on a dull or foggy day, contrast is much reduced. The range of brightness in the scene might then be only a couple of stops. Exposure errors have most effect in bright highlights and deep shadows, as these are the areas where a film is closest to the limits of its capability. Since these extremes are rarely encountered in low-contrast scenes, greater exposure error can be tolerated in images of this nature.

Exposure latitude is also sometimes equated to dynamic range, a measure of the range of exposure variation that a film, or indeed an electronic sensor, can tolerate without loss of image quality. At a certain point it no longer matters how much additional light reaches a recording medium, as its ability to record becomes exhausted. In the extreme case, a film exposed to daylight will be blank and exposure to even brighter light will make no difference. Similarly, there is a lower limit to the level of light that can be recorded. The difference between these points is correctly known as the dynamic range of the medium, but is also wrongly but perhaps more generally referred to as exposure latitude. Photographers must in any case aim to operate within it.

Various types of film exhibit different dynamic ranges, so latitude should be a consideration when choosing film for a particular purpose. Since slide films have less dynamic range than comparable colour negative films, perhaps five and seven stops respectively, they may be less satisfactory in conditions of extreme contrast. In general, colour films have less dynamic range than black-and-white films, and slow films have less than fast ones. The dynamic range of sensors used in digital cameras arguably lies between that of reversal and colour negative film, but precise figures are regarded as commercially confidential and are not released by manufacturers.


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