The Horseman Center Filter has a concentrically graduated center to eliminate the fall-off of illumination towards the corners of the lenses. It is designed to be used with ultra-wide-angle lens and is ideal for wide angle photography.This filter features a transparency, which radiates from the center and reaches full transparency at the filter’s edgesIt is advisable to avoid high contrast films, under-exposure, and non-uniform field illumination as much as possible while using ultra-wide-angle lensesThis  filter can be used with Horseman wide-angle lens units with 67mm filter threads