The PROND8 has a 3-stop light reduction equal to a ND optical density of 0.9. The ACCU-ND technology in the Hoya PROND filters yields a truly neutral color balance that will not add any noticeable color-cast to your images. The Hoya PROND series is aimed at the still photography and HDSLR video markets. The series provides 9 filters from two stop to 10 stop light reduction.