Abstract: For determining the extent of surface deterioration of a transparency, a method and apparatus is provided for measuring light scatter or halation produced by the deterioration. An intense light source is placed on one side of the transparency to be tested, and a camera and annular neutral density filter are positioned on the opposite side. The filter is aligned between the light source and camera lens so as to occlude or shade the lens from the direct light rays, whereby light scattered by portions of the transparency outside the periphery of the filter may be recorded on photographic film in the camera. The annular filter contains contrasting rings of varying shades of grey which facilitate standardization of halation measurements made on different transparencies or on the same transparency at different periods in its life cycle.