A densitometer (also called absorptiometer) is used to measure the density of a film by the amount of light which shines through; or tissue density (e.g., bone, lung) by the amount of radiation transmission. The logarithm of the reciprocal of the transmittance is called the absorbance or density.

A developer is a chemical solution that changes the film latent image to a visible image composed of black metallic silver.

The dipping method is a contact autoradiography of tissue using emulsion coated coverslips or x-ray films.

Fog in radiology refers to darkening of images by sources other than the radiation of the primary beam to which the film was exposed. This can be due to chemicals in the processing solutions, light, or non primary beam radiation.

The latent image is the invisible product of x-ray or photographic film emulsions, build after radiation or light exposure. The visible image is developed and fixed chemically from the latent image. Latent images are also produced in a photostimulable storage phosphor and retrieved by scanning with a laser.

See also Developer and Imaging Plate.