The sensitivity of X-ray film to direct X-ray exposure is low. To avoid large patient doses it is therefore desirable to use a more efficient imaging detector. This is accomplished by converting the X-ray image into light by means of a scintillating screen, also called X-ray intensifying screen, and then recording visible photons on film. The screen absorbs a large fraction of the incident X-rays and also provides signal amplification. The imaging properties of screen-film systems are reviewed in this chapter. Since the understanding of the physics of diagnostic radiology has evolved in parallel with the development of screen-film detectors this chapter also serves to introduce the fundamental physical parameters which define the quality of a radiographic image.