New Shutter Speed
1/100
Base speed
6 stops
ND 1.8 · ND64
ND Filter
Base Shutter Speed
This free long exposure calculator takes the guesswork out of ND filter photography. Select your base shutter speed — the metered exposure without any filter attached — then choose the number of stops your neutral density filter blocks. The calculator instantly outputs the correct long exposure time using the formula: New Shutter Speed = Base Speed × 2stops.
Once you have your target time, hit Startfor a 3-second countdown before the timer begins. This is especially useful for exposures that exceed your camera's built-in 30-second limit in bulb mode, and for keeping your hands off the camera during the exposure to avoid shake.
The calculator covers ND filters from 1 stop (ND2 / ND 0.3 density) through to 15 stops (ND32000 / ND 4.5 density), and base shutter speeds from 1/8000s all the way to 30s — every standard photographer shutter speed.
1-Stop · ND 0.3 · ND2
Subtle light reduction; balancing bright sky against foreground.
3-Stop · ND 0.9 · ND8
Silky water and gentle motion blur in bright outdoor light.
6-Stop · ND 1.8 · ND64
Smooth waterfalls and drifting clouds during the golden hour.
10-Stop · ND 3.0 · ND1000
Dramatic long exposures in full midday sun; creamy water.
13-Stop · ND 3.9 · ND8000
Ultra-long exposures measured in minutes; ghosting crowds.
15-Stop · ND 4.5 · ND32000
Extreme specialist work; 10+ minute daytime exposures.
The Formula
Each stop of ND glass halves the light reaching the sensor. To maintain the same exposure value, the shutter must stay open twice as long per stop. Result = Base Speed × 2stops.
Worked Example
Base speed 1/100s with a 10-stop ND1000: 1/100 × 210= 1/100 × 1024 ≈ 10.2 s.
Density Numbers
The optical density printed on most filters (e.g., ND 3.0) equals stops × 0.3. An ND 3.0 filter therefore blocks 10 stops of light.
