ND filter
calculator.
Pick your filter and base shutter speed, and get the new exposure time — plus the stops, optical density and light transmission. For long exposures and taming bright-light video.
Stacking filters adds their stops. Very long exposures can need a small reciprocity nudge on some sensors — meter and check your histogram.
ND filter chart
| Filter (ND number) | Stops | Optical density | Light transmitted |
|---|---|---|---|
| ND2 | 1 | 0.3 | 50% |
| ND4 | 2 | 0.6 | 25% |
| ND8 | 3 | 0.9 | 12.5% |
| ND16 | 4 | 1.2 | 6.25% |
| ND32 | 5 | 1.5 | 3.125% |
| ND64 | 6 | 1.8 | 1.563% |
| ND1000 | 10 | 3.0 | 0.098% |
| ND100000 | 16⅔ | 5.0 | 0.001% |
Keep the camera math in your pocket.
Set Math bundles ND, exposure, shutter and thirteen more calculators, free. DOPro puts them under a real director's viewfinder for the set.
ND filters, answered.
How do ND filter numbers relate to stops?
The ND number is how much it divides the light: ND2 is 1 stop, ND4 is 2, ND8 is 3 — each doubling adds a stop. ND1000 is about 10 stops. Optical density is stops × 0.301, so a 3-stop filter is density 0.9.
How do I calculate the new shutter speed?
Multiply your base shutter time by 2 to the power of the stops the filter cuts. A 1/125 s base with a 10-stop ND (×1024) becomes about 8 seconds — which the calculator above does for you.
What ND filter do I need for video?
Video shooters hold a 180° shutter (for example 1/48 s at 24fps) and add ND in bright light instead of stopping down or raising shutter. Meter how many stops you're over, then pick the ND that cuts that many. On set, DOPro keeps this to hand.