ABSTRACT
It is possible to obtain positive photographs directly on the material exposed in the camera. The first widely used photographic process, due to Daguerre, did produce positives directly. The first negative-positive process, due to Talbot, although announced at about the same time as that of Daguerre, gained ground rather more slowly, though today negative-positive processes are used for the production of the majority of photographs. Although processes giving positive photographs in a single operation appear attractive, in practice negative-positive
processes are useful because two stages are required. In the first place, the negative provides a master which can be filed for safe keeping. Secondly, it is easier to make copies from a transparent master than from a positive photograph, which is usually required to be on an opaque paper base. Also, the printing stage of a two-stage process gives an additional valuable opportunity for control of the finished picture. However, in professional work, especially colour, it has been the practice to produce transparencies, or direct positives, from which printing plates can be made for subsequent photomechanical printing. However, the advent of modern digital technology makes the application of the terms negative and positive less significant due to the ease with which images can be reversed (interchanged from negative to positive) and the ability to scan and digitize original photographic slides or prints.
