Hoya 77mm Variable Density Screw-in Filter;

This filter makes easy to adjust the brightness of a scene and have more control over the exposure settings of your camera, for both still photography and video use. The filter reduces light transmittance between approximately 1/3 and 1/400th of its original level, by rotating the inner filter ring. This allows a much greater range of shutter speed and aperture values to be set according to the desired effect. For example a long shutter speed can be used to blur water or crowds of people, even in full sunlight. The practical exposure range and light transmittance will vary depending on the situation.