# ND Filter Calculator

> Enter base shutter speed and ND filter strength to get adjusted exposure time

**Category:** Photography
**Keywords:** nd filter, neutral density, long exposure, shutter speed, photography, camera, exposure, stops, ND1000, ND64, bulb mode, landscape photography
**URL:** https://complete.tools/nd-filter-calculator

## How ND filters work

A neutral density filter is essentially a piece of dark glass that reduces the amount of light reaching your camera sensor without affecting color. Each stop of ND cuts the light in half, which means you need twice as long an exposure to capture the same brightness.

**The formula:**
```
New Exposure = Base Exposure × 2^stops
```

For example, with a base shutter speed of 1/250 s and an ND1000 filter (10 stops):
```
New Exposure = (1/250) × 2^10 = (1/250) × 1024 ≈ 4 seconds
```

Common ND filter conversions:
- ND2 (1 stop): doubles exposure time
- ND4 (2 stops): quadruples exposure time
- ND8 (3 stops): 8× longer exposure
- ND64 (6 stops): 64× longer exposure
- ND1000 (10 stops): 1024× longer exposure

## Why use ND filters

Neutral density filters let you use longer shutter speeds in bright conditions. This unlocks several creative techniques:

- **Silky waterfalls**: A 1-4 second exposure smooths out flowing water into a silky blur
- **Cloud motion**: Long exposures of 30 seconds to several minutes streak clouds across the sky
- **Removing crowds**: A 30+ second exposure makes moving people invisible in busy scenes
- **Shallow depth of field in daylight**: A wide aperture (f/1.4) in bright sun would normally overexpose — an ND filter lets you shoot wide open
- **Cinematic video**: The 180-degree shutter rule requires slower shutter speeds. An ND filter lets you follow this in bright conditions

## Choosing the right ND filter

- **ND2 to ND8 (1-3 stops)**: Subtle effects. Useful for shooting wide apertures outdoors or mild motion blur
- **ND64 (6 stops)**: The sweet spot for daytime long exposures of 1-5 seconds
- **ND1000 (10 stops)**: The most popular filter for dramatic long-exposure photography. Turns 1/250 s into ~4 seconds in most daylight conditions
- **ND32000 (15 stops)**: Extreme long exposures. Even midday sun yields multi-minute exposures

Variable ND filters let you dial in any strength, but can introduce color casts and X-patterns at extreme settings. Fixed ND filters are generally sharper and color-neutral.

## How to use

1. Set up your camera on a tripod and compose your shot
2. Meter the scene without the ND filter — note the shutter speed your camera suggests at your chosen aperture and ISO
3. Enter that base shutter speed into the calculator
4. Select your ND filter strength
5. The calculator shows the new exposure time
6. Attach the ND filter and set your camera to the calculated shutter speed
7. Use Bulb mode for exposures longer than 30 seconds, and a remote shutter release to avoid camera shake

## FAQs

**Q:** Do I need to adjust aperture or ISO too?


**A:** No — the ND filter calculation only affects shutter speed. Keep aperture and ISO the same as your base metered exposure.


**Q:** My camera only goes to 30 seconds. What do I do for longer exposures?


**A:** Use Bulb mode (B on the mode dial). Connect a remote shutter release or intervalometer to hold the shutter open for the exact duration. A phone timer works in a pinch.


**Q:** How accurate is the calculator?


**A:** The math is exact. Real-world results can vary slightly due to filter manufacturing tolerances (most ND1000 filters are actually 9.8-10.2 stops) and reciprocity failure at very long exposures with film.


**Q:** Can I stack ND filters?


**A:** Yes. Add the stop values together. An ND8 (3 stops) and ND64 (6 stops) stacked = 9 stops total. Be aware that stacking can introduce vignetting and reduce sharpness.


**Q:** What is the "exposure time" shown for very long values?


**A:** The calculator shows hours and minutes for exposures over 60 seconds. These extreme exposures (often 10-60 minutes) are used for light painting, star trails, and urban long exposures at dusk.

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