Inphotography, anegative is animage, usually on a strip or sheet of transparentplastic film, in which the lightest areas of the photographed subject appear darkest and the darkest areas appear lightest.[1] 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 subsequentphotographic processing.
In the case ofcolor negatives, the colors are also reversed into their respectivecomplementary colors. Typical color negatives have an overall dull orange tint due to an automatic color-masking feature that ultimately results in improved color reproduction.[2]
Negatives are normally used to make positive prints on photographic paper by projecting the negative onto the paper with aphotographic enlarger or making acontact print. The paper is also darkened in proportion to itsexposure to light, so a second reversal results which restores light and dark to their normal order.[3]
Negatives were once commonly madeon a thin sheet of glass rather than a plastic film, andsome of the earliest negatives were made on paper.[4]
Transparent positive prints can be made by printing a negative onto specialpositive film, as is done to make traditionalmotion picture film prints for use in theaters. Some films used in cameras are designed to be developed byreversal processing, which produces the final positive, instead of a negative, on the original film.[5] Positives on film or glass are known as transparencies or diapositives, and if mounted in small frames designed for use in aslide projector ormagnifying viewer they are commonly called slides.
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Apositive image is a normal image. A negative image is a total inversion, in which light areas appear dark and vice versa. A negative color image is additionallycolor-reversed,[6] with red areas appearing cyan, greens appearing magenta, and blues appearing yellow, and vice versa.
Under a phenomenon known as the 'negative picture illusion', a negative image can be briefly experienced by the human visual system where anafterimage persists subsequent to a prolonged gaze.
Film negatives usually have less contrast, but a widerdynamic range, than the final printed positive images. The contrast typically increases when they are printed ontophotographic 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.[7]
Film for cameras that use the35 mm still format is sold as a long strip ofemulsion-coated and perforatedplastic spooled in a light-tight cassette. Before eachexposure, a mechanism inside the camera is used to pull an unexposed area of the strip out of the cassette and into position behind thecamera lens. When all exposures have been made the strip is rewound into the cassette. After the film is chemicallydeveloped, the strip shows a series of small negative images. It is usually then cut into sections for easier handling.Medium format cameras use120 film, which yields a strip of negatives 60 mm wide, andlarge format cameras capture each image on a single sheet of film which may be as large as 20 x 25 cm (8 x 10 inches) or even larger. Each of these photographed images may be referred to as a negative and an entire strip or set of images may be collectively referred to as "the negatives". They are the master images, from which all positive prints will derive, so they are handled and stored with special care.
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 twonegative numbers in mathematics) a positive image results. This makes most chemical-based photography a two-step process, which usesnegative film andordinary 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)reversal films andreversal 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 ascyanotypes,gum bichromate,platinum prints, and many others.[8] Such negative images, however, can have less permanence and less accuracy in reproduction than their digital counterparts.[9]
A negative image can allow a different perception of an everyday scene, perhaps highlighting spatial relationships and details that are less obvious in the positive image. For example, the photographerAndrew Prokos has produced an award-winning series of photographs under the "inverted" banner.[10] The advent ofdigital image processing has expanded the possibilities. In a physical photograph the colour and luminance can only be inverted in tandem, but digital processing allows each to be inverted separately. If thehue of an image is rotated by 180 degrees, then the colour of the image is inverted but not its luminance. The negative of such an image has the luminance inverted but not the colour. Whereas a physical image can be either 'inverted' or 'not inverted', a digital image can exhibit a partial degree of colour inversion[11] in so far as the hue can be altered by plus or minus some number of degrees which is greater than zero degrees but less than 180 degrees.
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