PURPOSE: To use plural lenses of different control systems as the exclusive lenses by converting the drive system of a working lens unit into a controllable signal form and applying the prescribed correction to the AF control signal received from the main body of a video camera.

CONSTITUTION: A still camera lens unit SLS of a different type from a exclusive camera unit lens is attached to the camera unit (CM) via an conversion adaptor AD. Then the CM drives a focusing lens 1 of the SLS by a camera microcomputer 18, and the focus control instructions are sent to the AD for designation of the revolving direction, the revolving speed, the start/stop of revolution, etc., of the lens 1. Thus the AD performs the correction in response to the defocusing degree per pitch of the SLS, and a lens microcomputer 6 drives the lens 1 based on the output drive information. In such a constitution, plural SLS of different control systems are available as the exclusive lenses.