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.

The intrinsic conversion efficiency is the efficacy of an intensifying screen in converting x-rays into light photons.
For example, the radiation to light conversion efficiency of calcium tungstate is less than the efficiency of rare earth screens (about 5% vs. 12 - 18%).

Different types of screens are used in medical imaging. The intensifying screen or a pair of screens is used with x-ray film in radiography. Fluorescent screens coated with phosphor crystals emit light when exposed to radiation.