Photographic film Guide, Meaning , Facts, Information and Description
Photographic film is a sheet of plastic (polyester or cellulose acetate) coated with an emulsion containing light-sensitive silver halide salts (bonded by gelatin) with variable crystal sizes that determine the sensitivity or resolution of the film. When the emulsion is subjected to controlled exposure to light (or other forms of electromagnetic radiation such as X-rays), it forms a latent (invisible) image. Chemical processes can then be applied to the film to create a visible image; this process is called film developing.In black-and-white photographic film there is usually one layer of silver salts. When the exposed grains are developed, the silver salts are converted to metallic silver, which block light and appear as the black part of the film negative.
Color film uses at least three layers. Dyes added to the silver salts make the crystals sensitive to different colors. Typically the blue sensitive layer is on top followed by the green and red sensitive layers. During development, the silver salts are converted to metallic silver, as with black and white film. The by-products of this reaction form colored dyes. The silver is converted back to silver salts in the bleach step of development. It is removed from the film in the fix step.
Because photographic film was ubiquitous in the production of motion pictures, or movies, these are also known as films.
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2 History of film 3 Special films 4 Common sizes of film 5 Companies that manufacture photographic film 6 See also |
There are two primary types of photographic film:
Film basics
In order to produce a usable image, the film needs to be exposed properly. The range of tones that a given film can accurately record is called its exposure latitude. Color print film generally has better exposure latitude than other types of film. Additionally, because color print film must be printed to be viewed, some after-the-fact correction of the exposure can be made during the printing process.
Film speed describes a film's overall sensitivity to light. The international standard for for rating film speed is the ISO scale. Common film speeds include ISO 25, ISO 50, ISO 100, IS0 200, ISO 400, ISO 800, ISO 1600, and ISO 3200. Consumer print films are usually in the ISO 100 to ISO 800 range.
ISO 25 film is very "slow", so it requires much more exposure to produce a usable image than ISO 800 film. ISO 800, 1600 and 3200 film is thus better suited to low-light situations and action shots. The benefit of slow film is that it usually has finer grain and better colour rendition than fast film. Professional photographers usually seek these qualities, and therefore require a tripod to stabilize the camera for a longer exposure.
The first flexible photographic film was made by Eastman Kodak in 1885. This "film" was coated on paper. The first transparent plastic film was produced in 1889. Before this, glass photographic plates were used, which were far more expensive and cumbersome, albeit also of better quality. Early photography in the form of daguerreotypes did not use film at all.
Instant photography, as popularised by Polaroid, uses a special type of camera and film that automates and integrates development, without the need of further equipment or chemicals. This process is carried out immediately after exposure, as opposed to regular film, which is developed afterwards and requires additional chemicals. See instant film.
See also Film format.
This is an Article on Photographic film. Page Contains Information, Facts Details or Explanation Guide About Photographic film History of film
Special films
Common sizes of film
Companies that manufacture photographic film
See also