A radiation imaging system includes a two-dimensional array in which a plurality of elements which detect radiation are two-dimensionally arrayed. The plurality of elements includes a plurality of detectors usable for exposure control of stopping radiation irradiation in accordance with a fact that a radiation irradiation dose has reached a target irradiation dose. The radiation imaging system includes a controller configured to determine, based on a setting of a reading manner of signals from the plurality of detectors, a minimum irradiation time required from the start of radiation irradiation until the stop of radiation irradiation according to signals from the two-dimensional array and perform an error process when the minimum irradiation time exceeds a reference irradiation time.
