Reversal film

[1] 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).

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.

The earliest practical and commercially successful color photography reversal process was the Lumière Autochrome, introduced in 1907.

The final development process published by Kodak as K-14 involves multiple re-exposure steps to sensitize the unsensitized grains.

In late 1936, Agfacolor Neu was launched, Agfa having overcome earlier difficulties with color sensitivity problems.

The remaining silver halide salts are re-exposed to light, developed and fixed, and the film is washed and dried.

[8] Black-and-white transparencies were once popular for presentation of lecture materials using 3¼"×4" (3¼" square in the UK) glass-mounted slides.

Some projectors use a sliding mechanism to manually pull the transparency out of the side of the machine, where it is replaced by the next image.