Overview

Photographic film is a light-sensitive medium used to capture images of the world. Traditionally it is a flexible sheet or strip mounted on a supportive plastic base and coated with silver halide or other light-reactive layers. When exposed to a scene, light alters the chemistry of these layers so a latent image is recorded; that latent image becomes visible only after a controlled chemical treatment. Film was the dominant image-capture technology for much of the 20th century and remains in use today for artistic, archival, educational, and cinematic work.

Structure and how it records light

The typical film structure consists of a base, an emulsion layer, and protective coatings. The emulsion contains microscopic crystals that react to photons; the degree and pattern of reaction correspond to the brightness and distribution of the original visual scenes. Different emulsions are formulated for sensitivity, contrast, grain, and color rendition. Sensitivity is expressed by an ISO (formerly ASA) rating: higher numbers indicate greater light sensitivity but usually larger visible grain. Some films contain dyes or multiple emulsion layers to record color, while black-and-white films rely on metallic silver after processing.

Formats and physical variants

Film is available in many physical formats to suit different cameras and uses. Common formats include 35 millimeter cartridges for still photography, medium-format rolls and sheets for higher-resolution work, and large-format single sheets for technical and fine-art applications. Motion-picture film exists on wider, continuous rolls. Films are often supplied in light-tight canisters or wrapped packages to protect the unexposed emulsion until the moment of exposure.

Types of film

  • Black-and-white: Records luminance information; prized for tonality and archival stability.
  • Color negative: Produces an orange-tinted negative that is printed or scanned; common for general photography.
  • Color reversal (slide/transparency): Produces a direct positive image for projection or scanning.
  • Specialty films: Infrared-sensitive emulsions and high-resolution or low-grain stocks for technical work; see infrared film for one category.

Development and processing

After exposure, film must undergo chemical processing to convert the latent image into a visible and stable form. Basic black-and-white processing uses a developer to reduce exposed silver halide to metallic silver, a stop bath to halt development, and a fixer to remove unexposed salts and make the image no longer light-sensitive. Color negative film commonly uses a standardized process (C-41) and color reversal slides use processes such as E-6; each requires precise temperature and timing control. Many photographers process black-and-white film at home, while color processing is often done in labs. For more on methods and labs, see film processing.

History and continued relevance

Roll film and flexible film bases were popularized in the late 19th and early 20th centuries, enabling portable cameras and mass-market photography. Although digital imaging has largely superseded film for everyday use, analog film preserves characteristics valued by artists and archivists: the chemical grain, highlight rolloff, and archival longevity of properly processed emulsions. Film yields a different workflow and aesthetic; many educational programs and independent filmmakers continue to teach and practice film-based techniques alongside digital methods.

Notable facts and considerations

Choosing a film involves trade-offs among sensitivity, contrast, grain, and color response. Film must be stored away from heat and strong light and is sensitive to humidity; processed negatives and transparencies require proper archiving to prevent fading. Equipment for handling and scanning film remains widely available, allowing analog images to be digitized for editing, printing, and online sharing. For technical specifications or supplier information, consult resources on emulsion chemistry and format standards, or visit general references about light-sensitive materials and photographic technique.

Further reading and practical guides are available from community labs and manuals that cover exposure, metering, and darkroom technique; many online and local institutions continue to teach film photography basics and advanced processes (materials, composition, sensitivity, processing, specialty).