The Lee Seven 5 Reverse ND 1.2 (4 stop) is a neutral density filter with a smooth transition from dark to light from the middle of the filter upwards. It is particularly useful for seascapes when shooting bright horizons at sunrise or sunset, & is designed to give a more pleasing & natural balanced exposure to the sky. This 75x 90mm filter is also available in 0.6 & 0.9 ND strengths.