An optical system of the present invention includes a storage unit which stores an operated position of an operation unit and a position of an optical member. When the power supply to the optical system terminates and then restarts, a control unit compares the stored operated position and the operated position detected by a first sensing unit upon restart. If they are different, the control unit controls a driving unit such that the position of the optical member detected by a second sensing unit can be a target position. If they are the same, the control unit controls the driving unit such that the position of the optical member detected by the second sensing unit can be the stored position of the optical member.