In the early days of x-ray diagnosis the film used in the creation of x-rays pictures was standard silver halide film. This is similar to photographic film used in cameras. The difficulty in using this film for high energy x-rays is related to their penetrating power. The x-rays must penetrate human tissue and thus will also pass through most types of matter. Thus, most x-ray photons will go through the film and not be absorbed by the silver halide molecules. In most cases the standard film will absorb about 1% of the x-ray photons that strike it. The other 99% will penetrate passed through the film. Thus, to create an image that would be useful for medical diagnosis the patient needed to receive a very large dose of potential dangerous electromagnetic radiation.

The solution to this dilemma is to direct the x-rays to a material which converts them to visible light. The photons of visible light then strike the film and expose it. Because an x-ray photon’s energy is much higher than that of a photon of visible light, one x-ray photon can create several light photons. Further, dense materials which absorb a large fraction of the x-rays can be used. Thus, the x-ray dose that the patient receives is much smaller than it would be when the x-rays are absorbed directly by the film. An x-ray image that required 10-15 minutes to take during much of the early 20^th Century can now be completed in a fraction of a second.

Fluorescent materials are the key to making this process work. The x-rays are absorbed be a fluorescent layer. As described in the background section, the atoms and molecules in fluorescent material emit new photons in a serious of steps. In the case of converting ultraviolet light to visible light one visible and one infrared phtom are the usual result. For x-rays, several visible photons can appear. For practical reasons related to the sensitive fo the film, photons in the blue region of the spectrum are preferred.

Today’s images are captured in a film cassette which is a "sandwich" with the photographic film in the middle and a layer of fluorescent material on each side. These cassettes are frequently called image intensifiers because of the many photons which are emitted as a result of a single incoming x-ray.