Brass Ring for higher Quality Image Highest possible polishing technique World's best optical glass New thinner Pro mount. No vignetting USA Warranty This B+W Neutral Density Filter reduces the light intensity by three f-stops (log density 0.9). It still features very good color neutrality. This ND filter is especially appropriate for use on video cameras when the lens cannot be stopped down sufficiently in great brightness or when a deliberately low depth of field is desired. The filter factor is 8x.