The invention relates to a radiation screen for an X-ray device, comprising at least one radiation limiting means which is displaceably mounted and is embodied as a diaphragm. According to the invention, the radiation limiting means is displaceably mounted on a plane in a perpendicular manner in relation to a defining bundle of rays, and comprises a plurality of differently shaped diaphragm apertures for continuously limiting the different bundle of rays. It can, for example, be embodied as an essentially rotation-symmetrical perforated disk. In another embodiment, the radiation screen comprises two radiation defining means which are arranged in an overlapping manner in the direction of the bundle of rays which are to be defined.