ND Filter Calculator
Calculate new shutter speed for ND2 through ND1000 filters from your base exposure settings.
Returns adjusted time for waterfalls, traffic, and motion blur.
ND (Neutral Density) filters reduce the amount of light entering the camera without affecting color, allowing you to use slower shutter speeds or wider apertures in bright conditions for creative effects.
Stop calculation:
Stops = log₂(Filter Factor) or equivalently Stops = log(Filter Factor) / log(2)
Filtered Shutter Speed = Unfiltered Shutter Speed × Filter Factor
ND filter designation cross-reference:
| ND Label | Filter Factor | Stops | Light Blocked |
|---|---|---|---|
| ND2 | ×2 | 1 stop | 50% |
| ND4 | ×4 | 2 stops | 75% |
| ND8 | ×8 | 3 stops | 87.5% |
| ND16 | ×16 | 4 stops | 93.75% |
| ND64 | ×64 | 6 stops | 98.4% |
| ND256 | ×256 | 8 stops | 99.6% |
| ND1000 | ×1000 | 10 stops | 99.9% |
Worked example — Long exposure waterfall: Without filter: 1/500s shutter (bright daylight, f/8, ISO 100) Goal: 2-second exposure to blur water
- Required factor: 2s / (1/500s) = 2 × 500 = 1,000×
- Required filter: ND1000 (10-stop)
- Verification: 1/500 × 1,000 = 2 seconds ✓
Stacking ND filters: Stops add, factors multiply. ND8 (3 stops) + ND64 (6 stops) = 9 stops combined (factor = 8 × 64 = 512).
Creative uses by exposure length:
- 1/15 – 1/4 sec: Silky waterfalls
- 1–5 sec: Misty water, ghost movement of people
- 30 sec – 2 min: Cloud streaks, glass-flat water
- 2–10 min: Light trails, extreme seascape smoothing
Focusing tip: Always focus and compose before attaching an ND1000 — the viewfinder goes nearly black and autofocus struggles.