a first light-blocking unit that is movable between a charged position for closing a shutter aperture portion and a position for opening the shutter aperture portion;

a second light-blocking unit that is movable between a charged position for opening the shutter aperture portion and a position for closing the shutter aperture portion;

a charging member which charges the first and second light-blocking units and is movable at least between a first position in which the charging member maintains a charged state of the first light-blocking unit and a charged state of the second light-blocking unit and a second position in which the first and second light-blocking units are movable;

electromagnetic circuits to which the first and second light-blocking units are attachable so as to electrically support the first light-blocking unit in the charged state and the second light-blocking unit in the charged state, the electromagnetic circuits sequentially releasing the attached first and second light-blocking units so as to sequentially allow the first and second light-blocking units to move; and

a supporting member which protrudes into or recedes from a movement path of the second light-blocking unit in response to a movement of the charging member, the supporting member protruding into the movement path of the second light-blocking unit so as to maintain the second light-blocking unit in a state in which the shutter aperture portion is open.