ND Filter Exposure Calculator
Calculate required exposure time adjustments when using neutral density filters for long exposure photography
About this calculator
The ND Filter Exposure Calculator helps photographers determine the correct exposure time when using neutral density filters for long exposure photography. ND filters reduce light entering your camera, requiring longer shutter speeds to maintain proper exposure. This calculator automatically computes the adjusted exposure time based on your original settings and filter strength, eliminating guesswork and ensuring perfectly exposed long exposure shots of waterfalls, clouds, and motion blur effects.
How to use
Enter your original shutter speed without the ND filter and select your ND filter strength (measured in stops). The calculator will instantly display the new required exposure time. Use this adjusted time setting on your camera to achieve the same exposure level with your ND filter attached.
Frequently asked questions
What does ND filter strength in stops mean?
Each stop represents a halving of light. A 3-stop ND filter blocks 87.5% of light, requiring 8x longer exposure time than without the filter.
Can I stack multiple ND filters together?
Yes, you can stack ND filters. Add the stop values together (6-stop + 3-stop = 9-stop total) and use the combined value in the calculator.
Why do my long exposures sometimes come out overexposed?
Light conditions may change during long exposures, or your ND filter's actual strength may differ slightly from its rated value. Consider testing and bracketing exposures.