ND Filter Calculator

Pick your base shutter speed and ND filter — get the new long-exposure shutter speed, the stops added and the light-reduction factor, instantly.

Free Instant No sign-up

Your exposure

ND filter

Use a tripod and a remote release (or 2 s timer) for a sharp long exposure.

New shutter speed
0
0stops added
0ND factor
0% light passing
0s
Quick scenarios
0
—

How ND filter exposure is calculated

An NDx filter passes 1/x of the light, so the exposure needs x times longer:

New shutter = Base shutter × ND factor

The ND factor is the number in the filter's name: an ND8 multiplies the time by 8 and an ND1000 by 1000. In stops, factor ≈ 2stops: each stop halves the light, so an ND8 is 3 stops and an ND1000 about 10 (210 = 1024 ≈ 1000). That's why an ND1000 turns 1/125 s into several seconds. When you stack filters, the factors multiply and the stops add up. The tool also gives the percentage of light passing (100 ÷ factor), so you know exactly how much it darkens.

Example: a long exposure with an ND1000 filter

You shoot at 1/125 s and fit an ND1000 (about 10 stops):

  • ND factor = 1000× (≈ 210).
  • New shutter = 1/125 × 1000 = 8 s exposure.
  • Only 0.1% of the original light passes.

With an ND8 (3 stops), the same 1/125 s would only become 1/16 s — ideal for softening motion without darkening as much.

ND filter FAQ

How does an ND filter affect shutter speed?
An NDx passes 1/x of the light, so it multiplies the exposure time by x: an ND8 (3 stops) multiplies it by 8 and an ND1000 (about 10 stops) by 1000. Each stop doubles the time. The calculator does the conversion instantly.
What is an ND1000?
It is a filter that passes only 1/1000 of the light (0.1%): optical density 3.0, about 10 stops (9.97). It is used for long exposures in daylight: silky water, moving clouds, empty streets.
Which filter do I use for silky water?
It depends on the light: in moderate light an ND8-ND64 gets you to 1/4-1 s; in bright sun or for strong effects, an ND1000. Try the presets in the tool.
Can I stack several ND filters?
Yes: the factors multiply and the stops add up. An ND8 (3 stops) + an ND64 (6 stops) equals ×512, 9 stops. Watch for vignetting and possible colour cast when stacking.
Do I need a tripod for strong ND filters?
Essential. With multi-second exposures, the slightest movement ruins sharpness; use a tripod and a remote release or the 2-second timer.