A standard, diagnostic x-ray beam-limiting and shaping device with a motorized shutter/length adjustment mechanism that requires the operator to manually adjust the collimator shutters or length of the cone prior to an exposure in order to match the size and shape of the x-ray beam to the size of the x-ray cassette in use. Most motorized collimator assemblies include a light-centring device. An X-ray collimator is used to limit the effects of scattered radiation on image quality and to provide patient protection by eliminating exposure to non-target body areas.