1. A method of diagnostic imaging using a gamma ray detector including a scintillator array for emitting scintillation photons at photo conversion positions in response to incident gamma rays and a photodetector array coupled thereto in light-sharing mode for determining a spatial intensity distribution of scintillation photons, said method comprising: in a memory, recording spatial intensity distributions of scintillation photons emitted by the scintillator array in response to multiple incident gamma rays; with a computer, determining sets of coincidently emitted scintillation photons from the recorded spatial intensity distributions; with the computer, determining for the sets of coincidently emitted scintillation photons center-of-gravity positions and cumulative energies; with the computer, performing a clustering analysis based on the determined center-of-gravity positions and cumulative energies to obtain clusters of gamma ray events attributed to a scintillator array element; with the computer, cumulating for a cluster the spatial intensity distributions to determine a cumulative spatial intensity distribution of scintillation photons emitted in response to incident gamma rays in the scintillator array element; with the computer, determining a light matrix including expected spatial intensity distributions of scintillation photons for different scintillator array elements based on the cumulative spatial intensity distributions; generating spatial intensity distributions from gamma rays received from an imaged subject with the gamma ray detector; operating on the spatial intensity distributions using the light matrix to generate corrected spatial intensity distributions; and reconstructing the corrected spatial intensity distributions in a diagnostic image of the imaged subject.