1. An image capturing apparatus that couples a plurality of images so as to generate a composite image, comprising: an image capturing unit configured to capture images of an object; a determination unit configured determine, for each of a plurality of areas into which light receiving portions of the image capturing unit are separated, an exposure condition under which the image capturing unit is exposed; a first composition unit configured to couple to one another, area by area, the plurality of images that were shot by the image capturing unit under the exposure condition determined for each area by the determination unit, so as to generate a first plurality of composite images; and a second composition unit configured to compose the first plurality of composite images generated by the first composition unit so as to generate a single second composite image that has an extended dynamic range.