When a trigger lever is depressed, both a focus adjuster ring and a control disk commence to rotate in unison, driven by a spring mechanism. Position-sensing switches receive signals indicating which subject-distance setting the focus adjuster ring should be arrested at, and furthermore are opened and closed by the control disk during movement of the latter. When the focus adjuster ring reaches the required subject distance setting, it is arrested and kept arrested, thereby completing an automatic focussing operation, but the control disk continues to turn on to its end position, at which it causes the shutter mechanism of the camera to open and furthermore the exposure-timing circuit of the camera to initiation a scene-light-dependent exposure-timing operation.