An apparatus includes an imaging unit configured to photoelectrically convert an object image incident via a focus lens to acquire image data; a detection unit configured to detect a size and a position of an object based on the acquired image data; an adjustment unit configured to execute focus adjustment by acquiring a focus signal indicating a focusing state of the focus lens based on the image data while moving the focus lens, and moving the focus lens based on the focus signal; and a control unit configured to execute an operation if the detected size has changed, and to change the operation if the detected position has changed while the detected size has not changed.