In a case where illuminance is high, an error between the number of photons per frame calculated from time information and the number of photons and the actually expected number of photons per frame is reduced. In a time counter that counts a clock from the start of exposure in one frame, one-count time in the clock is switched depending on the illuminance. In a case where a pixel counter is saturated within a period of one frame, the illuminance is determined to be high, and a high-illuminance clock in which one-count time is set more minutely in the first half of one frame is used to count. In a case where the illuminance is not determined to be high, a normal clock is used to count.