An image sensor includes a plurality of pixels arranged in matrix, each pixel including a plurality of photoelectric conversion portions, and analog/digital converters configured to convert analog signals from pixels into digital signals provided by column. The analog/digital converter performs a first operation of converting an analog signal corresponding to the reset level into a digital signal, a second operation of converting analog signals obtained from some portions of the plurality of photoelectric conversion portions into digital signals, and a third operation of converting analog signals obtained from all the plurality of photoelectric conversion portions into digital signals.