[The effect of scattered radiation and tube focal size on the background density of x-ray pictures using an x-ray exposure system].

By experimental variation of scattered radiation (various field sizes with and without grid) it is shown, that even under defined experimental conditions there is little or negligible influence of scattered radiation on the photographic density of films. The variation is less than 5% for tube voltages between 55 and 120 kV (Exposure control system Robotron type 20041). Variations of film density connected with changes of focal spot size are explained by changes of kVp (insufficient tube load compensation) and by differences of energy sensitivity of ionization chambers and screen-film combinations as well as differences in exposure time for different focal sizes. Short exposure times below 200 ms and constant tube voltages result in equal film exposure, if different focal sizes are used.