Long Exposure Time Calculator
Calculate correct exposure time when using ND filters for long exposure photography
About this calculator
The Long Exposure Time Calculator helps photographers determine the correct exposure time when using neutral density (ND) filters for long exposure photography. ND filters reduce light entering your camera, requiring longer shutter speeds to achieve proper exposure. This calculator automatically computes the adjusted exposure time based on your original settings and ND filter strength, eliminating guesswork and ensuring perfectly exposed long exposure shots of flowing water, moving clouds, or light trails.
How to use
Enter your camera's base exposure time without the ND filter, then select your ND filter's strength (measured in stops). The calculator will instantly display the adjusted exposure time needed for proper exposure. Use this calculated time as your new shutter speed setting when shooting with the ND filter attached.
Frequently asked questions
What are ND filter stops?
ND filter stops indicate how much light the filter blocks. Each stop halves the light, so a 3-stop filter blocks 87.5% of light entering your lens.
Can I stack multiple ND filters?
Yes, you can stack ND filters. Add their stop values together (e.g., 3-stop + 6-stop = 9-stop total) and use the combined value in the calculator.
Why do my long exposures need such long times?
ND filters dramatically reduce light reaching your sensor. A 10-stop filter turns a 1-second exposure into over 16 minutes, creating smooth, ethereal effects.