A system which has two lens devices 10R and 10L and in which a baseline length of the lens devices 10R and 10L can be changed is equipped with a knob 60 for commanding of the degree of three-dimensionality; and a baseline length calculation unit 52 for calculating a baseline length that is most suitable to produce 3D video data that conforms to shooting conditions, being dependent on a subject to be shot by camera devices 20R and 20L, of the camera devices 20R and 20L to which the two lens devices 10R and 10L are attached with the degree of three-dimensionality specified by the knob 60 using information indicating the degree of three-dimensionality specified by the knob 60 and the shooting conditions, and outputting information of the calculated baseline length.