Abstract: In order to average out thermal noise but to magnify small value photon signals resulting from a gamma ray event in a scintillation camera having an array of photodetectors arranged in rows and column, the photon signals are summed for each row and summed for each column as a first step in the processing of the signals. As a second step the summed signals are weighted in accordance with an approximation to an energy distribution curve, and the weighted signals are then further weighted and summed for determining the position of the gamma ray event.