A lens apparatus includes a movable optical member, a position detection unit for detecting a position of the movable optical member, a control unit for recognizing position information obtained by the position detection unit and controlling driving of the movable optical member, and a signal input/output unit for synthesizing virtual and photographed pictures. The signal input/output unit can transmit the position information from the position detection unit linked with the movable optical member by three methods based on an analog voltage signal, a digital pulse train and data communication from the control unit.