An image sensor includes a pixel, the pixel has: a first photoelectric conversion unit and a second photoelectric conversion unit that photoelectrically convert light to generate a charge; an accumulation unit that accumulates at least one of the charge generated by the first photoelectric conversion unit and the charge generated by the second photoelectric conversion unit; a first output unit and a second output unit that output a signal based on the charge accumulated in the accumulation unit; and an adjustment unit that adjusts a capacitance of the accumulation unit if a signal based on the charges generated by the first photoelectric conversion unit and the second photoelectric conversion unit is output from the first output unit.