A reflecting element has at least one curved surface having a first plane of symmetry and being operative for reflecting incident light. A varying element is provided for varying the character of the reflector light and has a second symmetry paralleling the first plane. The elements are relatively moveable between an operative position and an inoperative position in which the varying element respectively varies and does not vary the character of light reflected by the reflecting element. An arrangement is provided for effecting such relative movement of the elements.