A camera and interchangeable lenses for such camera in which it is automatically detected whether or not the lens mounted on the camera has an automatic focusing capability. If it does, respective sets of electrical contacts provided on the lens and camera body are employed to transmit and receive a series of different data between the camera body and the lens. If it does not, the only a single datum is transmitted, for example, an open lens-stop value of the lens, is transmitted over the two sets of contacts. An automatic focusing actuation voltage applied from the camera body can be sensed to determine whether or not the lens has the automatic focusing capability.