Convert an ND filter's factor into stops and find the resulting shutter speed.
An ND filter reduces light by a factor, and its stops are the base-two logarithm of that factor, which slows the shutter correspondingly. Finding the stops lets you predict the long exposure needed for silky water or motion blur in bright conditions.
ND Filter Stops
Stops = log2(filter factor); shutter = base x 2^stops
Stops = log2(filter factor); shutter = base x 2^stops An ND filter reduces light by a factor, and its stops are the base-two logarithm of that factor, which slows the shutter correspondingly.
Finding the stops lets you predict the long exposure needed for silky water or motion blur in bright conditions.
This calculator takes 2 inputs: ND filter factor, Base shutter (1/x s). The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.