Opening the darkroom door may be disastrous, exposing someone s hard work or worse yet, an entire box of film. The all-encompassing term is darkroom etiquette. In some ways, we have gotten ahead of ourselves a bit. It has been mentioned several times that exposure of radiographic film occurs by interaction of x-ray photons or light photons. As it turns out, the latent image is created almost entirely by light photons.
Radiographic film is kept inside a film cassette.
Inside the film cassette are two phosphorescent intensifying screens . The film is tightly sandwiched between the two intensifying screens when the cassette is closed. The purpose of intensifying screens is to improve efficiency of the x-ray system so that less exposure to the patient and radiology personnel is possible. This is accomplished by a mechanism through which phosphorescent crystals of the screen convert energy carried by an x-ray photon into visible light photons. The phosphor crystals absorb a large percentage of the incoming x-ray photons and convert the absorbed energy into light.