Free calculator · runs in your browser

ND Filter & Long Exposure Calculator

Take your normal (un-filtered) shutter speed, add a neutral-density filter, and get the long-exposure time to use — for silky water, drifting clouds and empty streets. The same engine the Viewpoint app uses, in your browser.

Long-exposure time—
In seconds—
In the app

Time the long exposure to the light

A long exposure is only as good as the light you catch. Viewpoint plans the golden- and blue-hour windows for your spot and date, maps the sun and moon, and keeps it all working offline at the location. The ND math here is the same the app runs.

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How ND filters change your shutter

A neutral-density filter blocks light by a fixed number of stops. Each stop doubles the exposure time needed: a 10-stop filter turns a 1/60 s shutter into roughly 17 seconds. This calculator does that doubling for you — meter the scene without the filter, pick your ND strength, and read off the time to dial in (Bulb mode for the long ones).

Tips

  • Meter and focus first, then fit the filter — strong NDs make the viewfinder too dark to do either.
  • For exposures past ~30 s, switch to Bulb and a remote/timer.

Related

See the Exposure value calculator. Both are in the Viewpoint app.

For the stop math and gear, read Long exposure photography.

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