Photographic film is a recording medium consisting of a thin, flexible, transparent plastic base - typically made from cellulose acetate or polyester - coated on one side with a light-sensitive chemical emulsion. This emulsion is composed of microscopic silver halide crystals suspended in gelatin, which react when exposed to light, forming a latent image that is later revealed through the chemical development process.
Film comes in a variety of formats, including 35mm, medium format, and large format, each offering different image sizes and levels of detail. It is also available in a range of sensitivities, referred to as film speed or ISO rating, which determines how responsive the emulsion is to light. Lower ISO films produce finer grain and are suited to bright conditions, while higher ISO films are more sensitive and better suited to low-light situations but typically exhibit more visible grain.
Film can be broadly categorised as colour negative, colour reversal (slide film), or black and white, each with its own distinct characteristics, development processes, and aesthetic qualities. Despite the widespread adoption of digital photography, film continues to be used and valued by many photographers for its unique tonal qualities, texture, and the distinct look it imparts to images.