ND Filter Stops
Convert an ND filter's factor into stops and find the resulting shutter speed.
About ND Filter 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.
Formula
ND Filter Stops
Stops = log2(filter factor); shutter = base x 2^stops
- filter factor
- How many times the filter cuts the light
Worked example
With the default values below, ND Filter Stops returns Filter Stops of 9.97. Change any input above and every figure here is recalculated in your browser.
Inputs used
- ND filter factorminimum 1
- 1,000
- Base shutter (1/x s)minimum 1
- 125
Results
- Filter Stops
- 9.97
- Resulting Shutter (1/x s)
- 125,000
- Filter Rating
- 10 stop ND
Step by step
- 1Values used
- 2ND Filter Stops
- 3Filter Stops= 9.97
- 4Resulting Shutter (1/x s)= 125,000
- 5Filter Rating= 10 stop ND
Assumptions and limits
- The result is derived only from the 2 inputs listed above. Anything not among them is not part of the calculation.
- In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
- Figures are rounded for display to 2 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.
Frequently Asked Questions
How is ND Filter Stops calculated?
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.
Why does ND Filter Stops matter?
Finding the stops lets you predict the long exposure needed for silky water or motion blur in bright conditions.
What values do I need to enter?
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.