Abstract An x-ray sensitometer is used to measure the characteristic curve of radiographic films exposed with fluorescent intensifying screens. During exposure, x-ray kilovoltage, tube current, and exposure times remain constant. Radiation intensity is varied by automatic, stepwise increase of the focus-film distance. The x-ray source utilized a conventional radiation therapy x-ray machine modified for necessary output stability. Normally, 80 kVp x rays are used with 0.5 mm Cu + 3 mm Al filtration at the tube. Focal spot-film distance ranges from 10 to 126 inches. This exposure latitude gives a complete characteristic curve of film-screen systems with excellent reproducibility.