Imaging apparatus and method for controlling same

An imaging apparatus comprising:

• an imaging element in which pixel portions each having a plurality of photoelectric conversion units, which photoelectrically convert light fluxes having passed through different divided regions of an exit pupil of an imaging optical system to thereby generate image signals, with respect to one micro lens are arranged side by side in a horizontal direction and a vertical direction;
• an imaging element controller having a first mode which outputs a first left-eye image signal and/or right-eye image signal from the imaging element by composing signals from the plurality of photoelectric conversion units and a second mode which outputs signals without the composing;
• and
• a controller that outputs a second left-eye image signal and/or right-eye image signal by composing signals output in the second mode based on image data stored in a storage unit in response to the type of photographing for which the start has been detected.