Abstract: The invention relates to a radiodiagnostic apparatus with an x-ray tube, a diaphragm which is semitransparent at least areawise and which clears a slit variable in its width and letting the radiation go through, with an x-ray image intensifier and a television camera coupled thereto for the generation of video signals which is connected to a monitor for reproduction of the video signals. The diaphragm consists of several individual blades which abut against one another in parallel on both sides of the slit and are adjustable in longitudinal direction individually dependent on the size of the object to be viewed. To the television camera an evaluating circuit is connected which supplies a control signal obtained from the video signal to a setting device for the individual blades.