1
Every stop halves light
A 6-stop ND passes 1/64 of the light, which is why it turns harsh daylight into usable video exposure.
Stop math
ND Filter Calculator
Inputs
Example: enter 2000 for 1/2000 s and 50 for 1/50 s.
Results
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How to use this ND filter calculator
- Meter without ND. Enter the shutter speed your camera suggests before adding a filter.
- Pick your creative target. Choose the shutter speed you want for motion blur, shutter angle, or long exposure.
- Read stops and density. The calculator shows stop reduction, filter factor, and optical density notation.
- Round to real filters. Use the nearest common ND strength, then fine-tune ISO or aperture if needed.
- Stack carefully. Stacking filters works mathematically, but can add reflections, color shifts, and vignetting.
5 Fun Facts about ND Filters
2
ND 0.3 equals one stop
Optical density increases by 0.3 for each stop, so ND 1.8 is a 6-stop filter.
Density code
3
Variable ND uses polarizers
Most variable ND filters combine two polarizing layers, which can create cross patterns at extreme settings.
Filter design
4
IR pollution is real
Very strong ND filters may need IR control because some sensors see infrared contamination as muddy color.
Color caution
5
Long exposure eats time
A 10-stop filter turns 1/60 second into about 17 seconds, enough to blur water and clouds dramatically.
Slow shutter
About this ND filter calculator
Neutral density filters reduce light without intentionally changing color. They are essential when you want to keep a wide aperture or slow shutter speed in bright conditions. In video, ND is often the correct solution when a 180-degree shutter angle would otherwise overexpose the shot. In still photography, ND makes long exposures possible during daylight, letting moving water, clouds, traffic, and crowds blur while static subjects stay sharp.
This calculator compares your current metered shutter speed with your target shutter speed. The ratio between those two speeds becomes a filter factor, and the logarithm of that factor becomes stops. The optical density result is included because many filters are labeled ND 0.6, ND 1.2, or ND 1.8 instead of 2-stop, 4-stop, or 6-stop.
Use the nearest common filter result as a buying or packing guide. Real scenes still need judgment: variable ND filters can shift color, very strong filters may introduce infrared contamination, and stacked filters can vignette on wide lenses. Treat the output as the exposure math, then confirm with your camera histogram, false color, or waveform.
When planning a shoot, write down both the creative target and the filter value. That makes it easier to repeat a setup later, match multiple cameras, or explain why a specific ND was chosen for a shot.