ND long exposure calculator
Add an ND filter and get your new exposure time.
For film, add reciprocity failure on top for very long times.
About this tool
A neutral density filter cuts light so you can use long shutter speeds in daylight for smooth water or blurred clouds. This tool takes your base shutter speed and the ND filter strength in stops, then returns the new, longer exposure time. It saves you from guessing and from failed multi-minute frames.
How to use it
- Enter your base shutter speed measured without the ND filter attached.
- Select the ND filter strength in stops, for example 6 or 10 stops.
- Read the new exposure time the tool calculates.
- Switch to bulb mode with a timer if the time is longer than your camera's shutter range.
FAQ
How does ND strength relate to stops?
Each stop doubles the required time. A 10-stop ND multiplies your exposure time by about 1024, turning 1/60s into roughly 17 seconds.
Do I meter before or after fitting the filter?
Meter and focus first without the filter, then attach it and apply the calculated time. Dark NDs make metering and autofocus unreliable through the glass.