Work out neutral density filter stops instantly with clear inputs, formula shown and shareable results.
An ND factor of x reduces light by log2(x) stops, so the shutter speed must be multiplied by that same factor to keep the exposure unchanged. An ND64 is six stops, turning 1/125 into half a second, which is exactly what makes daylight long exposures of moving water possible.
Stops
stops = log2(ND factor)
New shutter speed
new time = base time x ND factor
stops = log2(ND factor). An ND factor of x reduces light by log2(x) stops, so the shutter speed must be multiplied by that same factor to keep the exposure unchanged.
An ND64 is six stops, turning 1/125 into half a second, which is exactly what makes daylight long exposures of moving water possible.
Enter nd filter factor, shutter speed without the filter. The defaults shown are a realistic worked example — swap in your own figures to get a result you can use.