Abstract: A camera system for communicating data between a micro computer on a camera body and a zoom lens mounted to the camera body, wherein at least exposure data on the diaphragm is transmitted from the zoom lens to the micro computer of the camera body, and wherein the zoom lens includes a position detecting device for detecting one of the divided focal length steps corresponding to a focal length of the zoom lens, a memory for storing data peculiar to the zoom lens, and an arithmetic operating device for calculating the exposure data on the diaphragm in accordance with the data of the position detecting device and the memory.