ND Filter Calculator

Calculate perfect exposure times with neutral density filters. Enter your base shutter speed and ND strength for both exact and rounded results.

Exact shutter time
Rounded shutter time
Total stops
Assumptions

Exposure time doubles for each stop. Rounding uses the nearest common shutter speed value. Long exposures display in seconds or minutes.

Worked Example

Scenario: Shooting a waterfall with a 6-stop ND filter

Base exposure: 1/60s at f/8, ISO 100

With 6-stop ND: 1/60 × 64 = 1.067s ≈ 1s

Result: Smooth, silky water motion instead of frozen droplets

FAQ

What is a stop?

One stop equals a doubling (or halving) of exposure time. A 3-stop ND filter reduces light by 8× (2³).

Can I stack filters?

Yes! Add the stops together. A 3-stop + 6-stop = 9-stop total reduction.

Why is rounding different from exact?

Real cameras use discrete shutter speeds. We choose the closest standard value for practical use.

What about variable ND filters?

Most variable NDs range from 2-8 stops. Check your filter's markings or test with a light meter.

Do I need to adjust aperture/ISO?

No, ND filters only affect shutter speed. Keep your aperture and ISO the same for equivalent exposure.

Related Tools

Equivalent Exposure Calculator · Astro Shutter Limit · Sunny 16 Rule

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