Exposure & ND Filter Calculator
Equivalent exposures, EV, and how long to leave the shutter open behind an ND.
How it works
Every exposure is a trade between three settings. Change one, and this calculator shows what the others must do to keep the same brightness — and how long the shutter needs to stay open once a neutral-density filter cuts the light. Times snap to the standard ⅓-stop scale your camera actually offers, with the exact figure alongside.
FAQ
- How does an ND filter change the shutter time?
- Each stop of neutral density halves the light, so the shutter doubles. A 10-stop ND1000 turns 1/60 s into about 17 seconds; a 6-stop ND64 turns 1/30 into 2 seconds. The calculator does the doubling and rounds to the nearest speed your camera has.
- What is EV?
- Exposure value is a single number for the light an aperture-and-shutter pair admits; EV 13 at ISO 100 is bright overcast, EV 15 is full sun, EV −6 is a moonless night. Two settings with the same EV give the same exposure.
- Why does the result differ slightly from my meter?
- Nominal shutter speeds are rounded (1/125 is really 1/128), so exact arithmetic drifts by a few hundredths of a stop. Your camera makes the same rounding.