High Quality Content by WIKIPEDIA articles! In photography, a reversal film is a type of photographic film that produces a positive image on a transparent base. The film is processed to produce transparencies, in contrast with negative and print. Reversal film is produced in various sizes, from 35 mm, roll film to 8x10" sheet film. A slide is a specially mounted individual transparency intended for projection onto a screen using a slide projector. This allows the photograph to be viewed by a large audience at once. The most common form is the 35 mm slide, placed inside a cardboard or plastic shell for projection. Reversal film is also used as motion picture film to yield a positive image on the camera original without an intervening negative.