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In photography, a negative is an Photograph, usually on a strip or sheet of transparent plastic film, in which the lightest areas of the photographed subject appear darkest and the darkest areas appear lightest. This reversed order occurs because the extremely light-sensitive chemicals a camera film must use to capture an image quickly enough for ordinary picture-taking are darkened, rather than bleached, by exposure to light and subsequent photographic processing.
In the case of color negatives, the colors are also reversed into their respective complementary colors. Typical color negatives have an overall dull orange tint due to an automatic color-masking feature that ultimately results in improved color reproduction.
Negatives are normally used to make positive prints on photographic paper by projecting the negative onto the paper with a photographic enlarger or making a contact print. The paper is also darkened in proportion to its exposure to light, so a second reversal results which restores light and dark to their normal order.
Negatives were once commonly made on a thin sheet of glass rather than a plastic film, and calotype were made on paper.
Transparent positive prints can be made by printing a negative onto special release print, as is done to make traditional motion picture film prints for use in theaters. Some films used in cameras are designed to be developed by reversal film, which produces the final positive, instead of a negative, on the original film. Positives on film or glass are known as transparencies or diapositives, and if mounted in small frames designed for use in a slide projector or Slide viewer they are commonly called slides.
Under a phenomenon known as the 'negative picture illusion', a negative image can be briefly experienced by the human visual system where an afterimage persists subsequent to a prolonged gaze.
Film negatives usually have less contrast, but a wider dynamic range, than the final printed positive images. The contrast typically increases when they are printed onto photographic paper. When negative film images are brought into the digital realm, their contrast may be adjusted at the time of scanning or, more usually, during subsequent post-processing.
Many photographic processes create negative images: the chemicals involved react when exposed to light, so that during development they produce deposits of microscopic dark silver particles or colored dyes in proportion to the amount of exposure. However, when a negative image is created from a negative image (just like multiplying two negative numbers in mathematics) a positive image results. This makes most chemical-based photography a two-step process, which uses negative film and ordinary processing. Special films and development processes have been devised so that positive images can be created directly on the film; these are called positive, or slide, or (perhaps confusingly) and reversal processing.
Despite the market's evolution away from film, there is still a desire and market for products which allow fine art photographers to produce negatives from digital images for their use in alternative processes such as , gum bichromate, platinum prints, and many others. Such negative images, however, can have less permanence and less accuracy in reproduction than their digital counterparts.
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