1. An image capturing apparatus comprising: an imaging lens; an image sensor that is composed of a plurality of two-dimensionally arranged pixels, the image sensor being configured to perform photoelectric conversion on incident light and output image data; a plurality of microlenses that are arranged between the imaging lens and the image sensor, each microlens corresponding to respective one of a plurality of regions of the image sensor, each region being composed of a predetermined number of pixels; an image processing unit configured to generate a reconstruction image at a predetermined refocus plane by performing refocus processing on the image data that was output from the image sensor, and determine whether or not a subject appears in the reconstruction image; and a recording unit configured to record the image data that was output from the image sensor and record information regarding the subject that was determined to appear by the image processing unit as auxiliary information in association with the image data.