Features: To enable slow shutter speeds to be used, especially with fast films, to record movement in subjects such as waterfalls, clouds, cars, seas, etc. To decrease depth of field by allowing wider apertures to be used, which helps separate subjects from their background. To decrease the effective ISO of high speed film (ie: above ISO400) and allow it to be used outdoors in blight situations. To allow cine and video cameras (which have fixed shutter speeds) to film subjects such as snow, sand or other bright scenes which would normally cause over-exposure. Specifications: Material: 1.5mm Optical Glass, Black Rimmed Frame (Thickness): 6.8mm Lens Diameter (mm): 52.0mm Suitable for: ALL CAMERAS Color: MATTE Black Anti-Lock Rim: 1mm Tips: The DIFFERENCE between ND filters & ND Grads ND filter works via a gray-coated glass. The main function of ND filter is to lower the exposure of the photos when taking. Suitable for taking photo(s) for bright items; Gradual-ND Filter (ND Grad) is a half-gray filter. It will keep the Color Balance but make contrasts. Suitable for scenery photos with the sky included or photos of the sky. You can turn the filter (glass/frame) to adjust the dirction of gray grads. The brightness of the sky would be lowered by the gray part to make balance with that of the ground. You can also apply this filter to take photos of clouds in the sky.