ND filter long exposure calculator
Meter without the filter, pick your ND filter and get the long exposure time — rounded to a shutter speed your camera has, or as a Bulb time with a countdown timer when it is longer than 30 seconds.
A base exposure of 1/60 s with ND1000 (10 stops) becomes 17 s. Set the shutter to 15 s (exact: 17 s).
1/60 s with other filters
| Filter | Exposure |
|---|---|
| 3 stops (ND8) | 1/8 s |
| 6 stops (ND64) | 1.1 s |
| 10 stops (ND1000) | 17 s |
| 15 stops (ND32000) | 9 min 6 s |
ND filter exposure chart
Base shutter speed (no filter) down the left; exposure time with each filter across.
| No filter | 3 stopsND8 | 6 stopsND64 | 10 stopsND1000 | 15 stopsND32000 |
|---|---|---|---|---|
| 1/1000 s | 1/125 s | 1/16 s | 1 s | 33 s |
| 1/500 s | 1/63 s | 1/8 s | 2 s | 1 min 6 s |
| 1/250 s | 1/31 s | 1/4 s | 4.1 s | 2 min 11 s |
| 1/125 s | 1/16 s | 0.5 s | 8.2 s | 4 min 22 s |
| 1/60 s | 1/8 s | 1.1 s | 17 s | 9 min 6 s |
| 1/30 s | 1/4 s | 2.1 s | 34 s | 18 min 12 s |
| 1/15 s | 0.5 s | 4.3 s | 1 min 8 s | 36 min 25 s |
| 1/8 s | 1 s | 8 s | 2 min 8 s | 1 h 8 min |
| 1/4 s | 2 s | 16 s | 4 min 16 s | 2 h 17 min |
| 0.5 s | 4 s | 32 s | 8 min 32 s | 4 h 33 min |
| 1 s | 8 s | 1 min 4 s | 17 min 4 s | 9 h 6 min |
Which ND filter do I need?
- 3 stops (ND8, 0.9) — slightly smoothed waterfalls in shade; wide apertures for portraits in bright sun; video at 1/50 s.
- 6 stops (ND64, 1.8) — silky rivers and waterfalls, blurred waves at sunset, 1–4 second exposures.
- 10 stops (ND1000, 3.0) — the classic long exposure: glassy seas and streaking clouds in daylight with 30 s–4 min exposures.
- 15 stops (ND32000, 4.5) — exposures of many minutes in full sun, removing moving people from busy scenes, and safe-ish solar setups (use a certified solar filter for the sun itself).
Step-by-step technique, including how to avoid light leaks and color casts, is in the ND filter long exposure guide. For every filter from ND2 to ND100000 with exact stops, optical density and times from 1/4000 s, see the ND filter chart.
How to use the nd filter calculator
- Meter without the filter. Compose, focus and set your aperture and ISO. Note the shutter speed that gives a correct exposure without the filter.
- Choose the filter. Select your ND filter strength — by stops, ND number or optical density — and add a second filter if you are stacking.
- Read the new time. The calculator shows the long exposure time. Up to 30 seconds, set it as the shutter speed; beyond that, switch to Bulb mode.
- Time the exposure. Use a remote release and start the built-in countdown timer when you open the shutter.
More photography calculators
- Depth of field calculatorNear and far limits of sharpness, with a diagram
- Hyperfocal distance calculatorWhere to focus so everything to infinity is sharp
- Equivalent exposure calculatorTrade aperture, shutter and ISO at the same brightness
- Crop factor calculatorEquivalent focal length, aperture and field of view
- 500 rule & NPF calculatorLongest exposure for pinpoint stars
Frequently asked questions
How do I calculate exposure time with an ND filter?
Multiply your normal shutter speed by 2 for every stop the filter blocks: new time = base time × 2^stops. With a 10-stop filter (ND1000), 1/60 s becomes 1/60 × 1,024 ≈ 17 seconds; with a 6-stop filter (ND64), 1/125 s becomes about 1/2 s.
How do ND numbers, stops and optical density relate?
The ND number is the light reduction factor, the stop count is log₂ of that factor and optical density adds 0.3 per stop. ND8 = 3 stops = 0.9; ND64 = 6 stops = 1.8; ND1000 = 10 stops = 3.0; ND32000 = 15 stops = 4.5. Manufacturers round: ND1000 is really 9.97 stops.
What happens when I stack two ND filters?
Their stops add up (the factors multiply): an ND8 (3 stops) plus an ND64 (6 stops) is 9 stops, or 512×. Stacking increases the risk of vignetting on wide lenses and of a color cast, so a single strong filter is usually better.
How do I focus and meter with a 10-stop filter?
Compose, focus and meter without the filter, then switch to manual focus and manual exposure, attach the filter and set the calculated time. The viewfinder will be almost black, and autofocus and metering are unreliable through very dense filters.
Why is my long exposure too dark or has a color cast?
Real filters are often 1/3 stop off their nominal strength, and many strong ND filters add a blue or warm tint. Take a test shot, check the histogram, and correct the white balance in RAW. Cover the optical viewfinder during long exposures to stop light leaking in.