Image capturing apparatus and control method thereof

A method for controlling an image capturing apparatus, comprising:

• a reading step of, from an imaging device configured to receive light fluxes passing through different areas of an exit pupil of an optical system independently and output an image signal obtained therefrom, reading out the image signal corresponding to each the different areas of the exit pupil;
• a calculation step of calculating a correction value for the image signal corresponding to each of the different areas of the exit pupil read in the reading step to correct an influence from vignetting on the light fluxes due to shift of a shake correction unit in response to activation of the shake correction unit which corrects an image blur corresponding to a shake amount exerted on the image capturing apparatus;
• a correction step of correcting the image signal corresponding to each of the different areas of the exit pupil using the correction value calculated in the calculation step;
• and
• a focus control step of performing focus control on a basis of a phase difference between the image signals of corresponding to different areas of the exit pupil, the image signals subjected to correction in the correction step.