A positive is a photographic image in which the tonal values and, in colour materials, the colours of the recorded subject correspond directly to those of the original scene - bright areas of the subject are rendered as light tones in the image, dark areas are rendered as dark tones, and colours appear in their correct, natural hues rather than in their complementary opposites. This direct correspondence between the tones and colours of the image and those of the original subject distinguishes a positive from a negative, in which tones are reversed - highlights appear dark and shadows appear light - and colours, in colour negative materials, are represented as their complementary opposites.
Photographic positives are encountered in several distinct forms, each produced by a different process and suited to different purposes and applications. The most familiar form of positive image in everyday photographic practice is the conventional photographic print - a positive image produced on photographic paper by printing from a negative, in which the tonal reversal of the negative is reversed a second time to restore the correct tonal relationships of the original subject. Prints are the standard medium for the display, sharing, and archiving of photographic images, and the vast majority of photographs seen in publications, on walls, and in personal collections take the form of positive prints produced from negative originals.
Transparencies, also commonly known as slides or reversal film, represent a second major category of positive photographic image, in which a positive image is formed directly on the film itself rather than on a separate paper support. Unlike negative film, which produces a negative image requiring a printing stage to produce a positive result, reversal film is processed through a chemical sequence that reverses the initial negative image formed during exposure back to a positive, producing a transparency in which the tones and colours of the original subject are correctly represented directly on the developed film. Transparencies are intended to be viewed by transmitted light - either by holding them up to a light source, placing them on a lightbox, or projecting them with a slide projector - and their tonal and colour rendering has a luminosity and richness, particularly in the highlights and saturated colours, that reflected light print viewing cannot fully replicate.
The distinction between positive and negative images is fundamental to understanding the basic chemistry and workflow of traditional photography, as virtually all photographic systems - whether based on silver halide, alternative processes, or digital capture - can be characterised in terms of whether they produce positive or negative images, and whether any subsequent printing or processing stage is required to derive a positive viewing image from the original capture medium. In digital photography, the captured image data can be viewed as a positive image immediately on the camera's LCD screen or electronic viewfinder, and the digital file produced by the camera represents a positive image regardless of whether the original exposure information is stored in a processed JPEG format or in the raw, unprocessed form of a RAW file.