1. An exposure control system for use in a scintillation camera couplable to an image sensing camera and having a display apparatus responsive to radiation signals representing the position of radiation stimuli to produce and expose to the image sensing camera an image representing the positional location of the stimuli, said image being adjustable in intensity independently of said radiation signals, and a detector having a predetermined field of view and being responsive to the radiation stimuli to produce the radiation signals, said exposure control system comprising: a. an information control circuit connected to the detector for controlling the amount of exposure of the image to the image sensing camera by terminating the exposure in response to the accumulation of a predetermined quantity of radiation occurring within a predetermined zone of said detector field, b. a circuit connected to said information control circuit for producing an index representing the value of said quantity of radiation, said representation further being controllable as a function of said independent intensity adjustment of said display apparatus, and c. a circuit for indicating the value of said index representation to enable calibration of the image intensity by varying said independent intensity adjustment in accordance with said quantity of radiation and said exposure amount to maintain the detectability of the image by the image sensing camera. pg,41