ND Filter Calculator

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:

That last row is not a typo. Ten stops is a factor of 2¹⁰ = 1024, not 1000. Manufacturers round the name down because “ND1000” sells better than “ND1024”, and every other filter in the range is named for its exact factor. The calculator uses 1024, because that is what the glass does. The difference is 0.03 of a stop, which matters to nobody, but a page that says ×1000 and prints ×1024 is just confusing.

While we are on the subject of nominal numbers: a 10-stop filter is rarely exactly 10 stops. Cheaper ones drift a third of a stop or more, and most of them add a colour cast, usually magenta or cyan, that you fix in raw. Shoot one test frame and note your filter’s real offset once, then apply it forever.

Worked example, a long-exposure waterfall: Without filter: 1/500s shutter (bright daylight, f/8, ISO 100) Goal: about a 2-second exposure to blur water

• Required factor: 2s ÷ (1/500s) = 2 × 500 = 1,000×
• Nearest filter: ND1000 (10-stop, really ×1024)
• Result: 1/500 × 1024 = 2.05 seconds, which is the 2 seconds you wanted

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.