Hoya 77mm Variable Neutral Density FilterThe Hoya 77mm Variable Neutral Density Filter is a solid variable neutral density filter providing an exposure reduction of about 1. 5 to 9 stops. The 0. 45 to 2. 7 density creates a darkening of the entire image, allowing you to photograph with a wider aperture or slower shutter speed than would normally be required. The degree of density is easily controlled by rotating the front filter ring, helping you to predetermine the additional exposure