ND Filter Stops & Exposure Time
Convert ND filter strength between ND factor, stops and optical density and find the new shutter speed, free online.
About this calculator
An ND filter cuts light by a factor: ND8 = 3 stops = optical density 0.9; ND64 = 6 stops = 1.8; ND1000 = 10 stops = 3.0. The new exposure time = original time × ND factor, so 1/125 s becomes 8 s with an ND1000.