Sheet film is large format and medium format photographic film supplied on individual sheets of acetate or polyester film base rather than rolls. Sheet film was initially supplied as an alternative to glass plates. The most popular size measures 100 mm × 130 mm (4 in × 5 in); smaller and larger sizes including the gigantic 510 mm × 610 mm (20 in × 24 in) have been made and many are still available today.
In photography, reversal film, or slide film, is a type of photographic film that produces a positive image on a transparent base. Instead of negatives and prints, reversal film is processed to produce transparencies, or diapositives (abbreviated as "diafilm" or "dia" in some languages like German, Romanian or Hungarian). Reversal film is produced in various sizes, from 35 mm to roll film to 8×10 inch 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, with the image framed in a 2×2 inch cardboard or plastic mount. Some specialized labs produce photographic slides from digital camera images in formats such as JPEG, from computer-generated presentation graphics, and from a wide variety of physical source material such as fingerprints, microscopic sections, paper documents, astronomical images, etc.
Roll film or rollfilm is any type of spool-wound photographic film protected from white light exposure by a paper backing. The term originated in contrast to sheet film. Confusingly, roll film was originally often referred to as "cartridge" film because of its resemblance to a shotgun cartridge.
The opaque backing paper allows roll film to be loaded in daylight. It is typically printed with frame number markings which can be viewed through a small red window at the rear of the camera. A spool of roll film is usually loaded on one side of the camera and pulled across to an identical take up spool on the other side of the shutter as exposures are made. When the roll is fully exposed, the take up spool is removed for processing and the empty spool on which the film was originally wound is moved to the other side, becoming the take up spool for the next roll of film.
A film holder is a accessory that holds one or more pieces of photographic film, for insertion into a camera or optical scanning device such as a dedicated film scanner or a flatbed scanner with film scanning capabilities. The widest use of the term refers to a device that holds sheet film for use in large format cameras, but it can also refer to various interchangeable devices in medium format or even 135 film camera systems.