Abstract: The present invention teaches a method for uniformly flooding a nuclear imaging device with radiation from a radiation-emitting calibration source and for correcting for the non-uniformity in count density of nuclear imaging sources and apparatus for carrying out the method. The method includes the steps of positioning a nuclear imaging flood source beneath or adjacent a nuclear imaging device such as a gamma camera having a plurality of radiation sensing elements; moving the source in a controlled motion; thereby blurring or diminishing the effects of any non-uniformities in the source. Apparatus for moving the source includes a support for the source and a means for moving the source adjacent to or beneath a camera. Circular motion may be achieved by connecting the support to means for rotating it, such as a motor drive shaft, or by manually rotating it. Other simple motion may be achieved by means which move the source about a simple curve.