A camera includes a photographic optical system movable along its optical axis, and a cam ring rotatable about the optical axis of the optical system. When it is rotated by a motor, the cam ring moves the optical system to change the focal length thereof. Arranged at the outside of the cam ring are a viewfinder optical system, whose optical axis is parallel to that of the photographic optical system, and a strobe mechanism movable in a direction parallel to the optical axis of the photographic optical system. First and second cam portions are arranged on the cam ring and engage the viewfinder optical system and strobe mechanism, respectively, so as to move them along the optical axis of the photographic optical system, in association with the rotation of the cam ring.