A light quantity adjustment apparatus includes a support plate with a first through hole, a rotation plate with a second through hole corresponding to the first through hole and rotatable with respect to the support plate, 2D iris plates rotatably connected to the support plate so as to move between a location in which the first through hole is completely opened and another location in which the first through hole is completely closed, two 3D iris plates each having one end rotatably connected to the support plate and another end engaged with the rotation plate, a shading plate, and a shading plate driving unit. The 2D iris plates adjust an open area of the first through hole. The two 3D iris plates move between a retreat location away from the first through hole and a photographing location where a first photographing hole and a second photographing hole are formed.