A film consists of a thin, transparent sheet of polyester or similar material. Films are coated on one or both sides with an emulsion sensitive to radiation, light or heat. Films are relatively radiolucent due to their relatively low atomic number (that of silver halide).

See also X-Ray Film, Direct Exposure Film and Intensifying Screen.

An x-ray film is a photographic film used to generate a visual x-ray image. X-ray films are rarely used as the only radiation detector. Commonly they are used in conjunction with intensifying screens placed in the film cassette, because high resolution films have a poor sensitivity to x-rays. At direct film exposure, only a small amount of x-ray photons will be absorbed and react with the film emulsion. An intensifying screen contains scintillating materials to convert x-ray radiation into light or lows electromagnetic energies.
X-ray films provide very good spatial resolution and contrast, but need long exposures times and chemical processing.

See also Conventional Radiography and Digital Radiography.

The film contrast is the ability of a film to translate contrast of various tissues to differences in the resulting image. Film contrast depends on both film characteristics and processing.

A film processor is a peripheral x-ray equipment used in conjunction with a camera to create hard-copy images. Film processors should be maintained at their optimum operating conditions by regular quality control procedures. Optimal film processing has important implications for the diagnostic quality of the image stored on film.

Direct exposure films are highly sensitive to the direct effect of x-rays rather than in combination with an intensifying screen. However, a film is a relatively inefficient radiation detector and requires relatively high radiation exposure. The use of rectangular collimation and the highest speed films reduce radiation exposure.

See also Conventional Radiography.