An image sensor includes: a first pixel having a first photoelectric conversion unit that photoelectrically converts light to generate a charge, a first accumulation unit that accumulates the charge generated by the first photoelectric conversion unit, and a first output unit that is connected to the first accumulation unit; a second pixel having a second photoelectric conversion unit that photoelectrically converts light to generate a charge, a second accumulation unit that accumulates the charge generated by the second photoelectric conversion unit, and a second output unit that is connected to and disconnected from the second accumulation unit via a second connection unit; and an adjustment unit that adjusts capacitances of the first accumulation unit and the second 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.