Abstract: A radiation absorption shield assembly is disclosed for controlling the configuration of the radiation sensitive field of a radiation detecting camera. The shield assembly includes a first annular lead shield element defining a first aperture and mounted to the camera for blocking out a fixed field of radiation. The assembly also includes a second annular lead shield element in series with the first which defines a second aperture movable with respect to the first aperture. Attached to and in a spaced parallel relation with the first shield element is a circular radiation transparent disk which defines a thin gap to accommodate the second shield element. The second shield element is slidably adjustable within the gap, transverse to the first element, by one conducting a radiation study, to vary the configuration of a region of interest defining a field area through which radiation can pass from the patient for detection by the camera.