the present invention relates to a camera system having an auto - focusing device which carries out a so - called overlapped operation in which storing of a light signal by a focus sensor and calculation of a lens drive distance based on the stored value are performed while a lens is driven . in the present invention , where a lens system mounted on the camera does not have a characteristic suitable to the overlapped operation , it is automatically detected and the overlapped operation is inhibited to prevent improper proceeding of the overlapped operation .