Image capturing apparatus and method for controlling the image capturing apparatus

An image capturing apparatus comprises an image sensor that includes a plurality of pixels each having a plurality of photoelectric conversion units and a microlens and that is capable of capturing a subject and periodically outputting image signals individually from the plurality of photoelectric conversion units, a control unit that performs control such that, within the period in which the image sensor outputs an image signal, charge accumulation durations of the plurality of photoelectric conversion units of each pixel of the image sensor are shifted with respect to each other, and a synthesizing unit that sums up, for each pixel, the image signals individually output from the plurality of photoelectric conversion units.