Reversal film

In photography, the terms reversal film, slide film, positive film, and transparency film describe a type of photographic film that produces a positive image on a transparent film base. In place of negatives and printed photographs, reversal film produces , known as diafilm and dia images. A diapositive slide is a mounted frame of transparency film intended for large-format projection of the image onto a screen by a slide projector. Such large-format projection permits many spectators to view the diapositive image at one time. The usual transparency-film format is the 35 mm slide, wherein one frame of film is mounted into a 2 in. ×2 in. square made either of cardboard or of a plastic material. Reversal film is produced in format sizes that range from 35 mm to roll film to 8 in. ×10 in. sheet film.

Moreover, specialized photographic processing laboratories produce diapositive slides from digital-camera images in formats such as the JPEG, from computer-generated presentation graphics, and from images of physical materials such as fingerprints, microscopic evidence, paper documents, astronomic images, etc. Reversal film also is used as motion picture film in the 16 mm, Super 8 and 8 mmcine film formats, and produces a positive-image film that was originated in the cinematographic camera. In terms of film-production costs, such a cinematographic application of reversal film is more cost-effective than filming with negative film that then must be developed into a positive-image film for projection in a cinema.