A camera system comprising an interchangeable lens including an imaging optical system including a focus lens, and a camera main body to which the interchangeable lens is detachably attached, wherein the interchangeable lens comprises a lens side storage unit that: is configured to store pupil related data according to an image height (x), and wherein the camera main body comprises: an image sensor including a plurality of imaging pixels for imaging, and a plurality of focus detection pixels for focus detection; a main body side storage unit that is configured to store correction data for correcting non-uniformity in illumination distribution by incident light to the focus detection pixels based on outputs of the focus detection pixels; and a correction unit that is configured to receive the pupil related data from the lens side storage unit, and correct non-uniformity in illumination distribution of outputs of the focus detection pixels based on the correction data, the pupil related data, and the image height (x), wherein the camera system is characterized in that the pupil related data is data regarding a corrected F-number of the interchangeable lens and data regarding a corrected exit pupil position of the interchangeable lens, wherein the data regarding the corrected F-number of the interchangeable lens indicates a range of luminous flux to be applied to the focus detection pixels at a predetermined image height (x), wherein the data regarding the corrected exit pupil position of the interchangeable lens relates to a position of intersection of a center of luminous flux applied to the focus detection pixels at a predetermined image height (x) and an optical axis of the imaging optical system, and wherein the main body side storage unit is configured to store the correction data corresponding to both of data regarding the corrected F-number and data regarding the corrected exit pupil position, wherein the corrected F-number and the corrected exit pupil position are each corrected in accordance with the image height (x). an image sensor including a plurality of imaging pixels for imaging, and a plurality of focus detection pixels for focus detection; a main body side storage unit that is configured to store correction data for correcting non-uniformity in illumination distribution by incident light to the focus detection pixels based on outputs of the focus detection pixels; and a correction unit that is configured to receive the pupil related data from the lens side storage unit, and correct non-uniformity in illumination distribution of outputs of the focus detection pixels based on the correction data, the pupil related data, and the image height (x), wherein the camera system is characterized in that the pupil related data is data regarding a corrected F-number of the interchangeable lens and data regarding a corrected exit pupil position of the interchangeable lens, wherein the data regarding the corrected F-number of the interchangeable lens indicates a range of luminous flux to be applied to the focus detection pixels at a predetermined image height (x), wherein the data regarding the corrected exit pupil position of the interchangeable lens relates to a position of intersection of a center of luminous flux applied to the focus detection pixels at a predetermined image height (x) and an optical axis of the imaging optical system, and wherein the main body side storage unit is configured to store the correction data corresponding to both of data regarding the corrected F-number and data regarding the corrected exit pupil position, wherein the corrected F-number and the corrected exit pupil position are each corrected in accordance with the image height (x).