Long Exposure Time Calculator

Enter your base shutter speed and ND filter strength to calculate the new exposure time, light reduction factor, optical density, and more.

Created by Luis GonzalezLast updated: May 9, 2026

How to Use This Calculator

1
Input Base Shutter Speed
Enter your camera's metered shutter speed (in seconds) without any ND filter attached. For example, 0.008 for 1/125s, or 1 for 1 second.
2
Specify ND Filter Strength
Enter the number of stops your primary Neutral Density (ND) filter blocks. Common filters include 6 stops (ND64) or 10 stops (ND1000).
3
Add Extra Stacked Stops
If you're using additional filters (like a polarizer or another ND filter), input their combined stop value. Enter 0 if no additional filters are stacked.
4
Review Your New Exposure Time
The calculator will display the resulting long exposure time in seconds and minutes, along with other optical properties.

Example Calculation

A landscape photographer wants to achieve a silky water effect. Their camera meters a base shutter speed of 1/125s (0.008s) without a filter, and they plan to use a 6-stop ND filter.

Base Shutter Speed (s)

0.008

ND Filter Strength (stops)

Extra Stacked Stops (stops)

Results

0.512 s

Tips

Account for Reciprocity Failure

For exposures longer than 30 seconds, film and some digital sensors exhibit reciprocity failure, requiring even longer exposure times than calculated. Add an extra 10-20% for exposures over 1 minute, and more for multi-minute shots, to compensate for light loss.

Use a Remote Shutter Release

To avoid camera shake during long exposures, especially those lasting several seconds or minutes, use a remote shutter release or your camera's 2-second timer. Any physical contact with the camera can introduce blur.

Bracket Your Exposures for Safety

When shooting very long exposures, especially in changing light conditions, take several shots at slightly different exposure times (e.g., +/- 1/3 or 1/2 stop). This increases your chances of capturing the perfect amount of motion blur and ensures you have a usable image. For a target of 0.512s, try shots at 0.4s and 0.6s.

Unlocking Creative Vision with Your Long Exposure Time Calculator

The Long Exposure Time Calculator is an essential tool for photographers looking to master the art of long exposure photography. It precisely calculates the required shutter speed when using Neutral Density (ND) filters, even with stacked filters, revealing the optical density, light transmission, and appropriate exposure category. This empowers you to achieve stunning effects like silky smooth water or dramatic light trails. For instance, transforming a quick 1/125s shot into a flowing 0.5-second capture for moving water becomes effortless.

Mastering Creative Effects with Long Exposures

Long exposure photography is a powerful technique for transforming ordinary scenes into captivating, ethereal images. By allowing the camera's shutter to remain open for an extended duration, typically from 1 second to several minutes, photographers can capture motion as a blur while keeping stationary elements sharp. This creates specific artistic effects: silky smooth water and clouds (often requiring 1-30 seconds), dramatic light trails from vehicles at night (5-60 seconds), or even ghosting effects in busy public spaces by making moving people disappear with multi-minute exposures. To achieve these, equipment beyond ND filters is crucial, including a sturdy tripod to prevent camera shake and a remote shutter release. Understanding these effects allows photographers to choose the optimal shutter speed, transforming a mundane scene into a dynamic piece of art.

The Exposure Math Behind ND Filters

The calculation of long exposure time with ND filters is based on the principle of light reduction in "stops." Each stop of light reduction effectively doubles the exposure time needed to achieve the same brightness.

The core formula involves:

Total Stops: Sum of the primary ND filter's stops and any additional stacked filter stops.
```
Total Stops = ND Filter Strength (stops) + Extra Stacked Stops (stops)
```
Light Reduction Multiplier: This is 2 raised to the power of the total stops.
```
Multiplier = 2 ^ Total Stops
```
New Exposure Time: Multiply the base shutter speed by the multiplier.
```
New Exposure Time = Base Shutter Speed (s) × Multiplier
```
For example, a 6-stop filter has a multiplier of 2^6 = 64. This means it will increase your exposure time by 64 times.

💡 To ensure your subject is in sharp focus even with a long exposure, our Subject Distance to Depth of Field Calculator can help you set your aperture and focus point precisely.

Practical Long Exposure Calculation: A River Scene

Consider a photographer setting up by a river, aiming for a soft, flowing water effect. Without any filters, their camera meters the scene at a base shutter speed of 1/125th of a second (0.008s). They decide to use a 6-stop ND filter to dramatically extend the exposure.

Here's how they calculate the new shutter speed:

Determine Total Stops: The primary filter is 6 stops, and there are no stacked filters, so Total Stops = 6 + 0 = 6.
Calculate Light Reduction Multiplier: Multiplier = 2 ^ 6 = 64.
Compute New Exposure Time: New Exposure Time = 0.008 seconds × 64 = 0.512 seconds.

The calculator reveals that their new exposure time will be 0.512 seconds, which is just over half a second. This duration is perfect for blurring moving water while keeping the surrounding landscape sharp, achieving that desired silky effect.

💡 For quick exposure estimates in bright conditions without a meter or ND filters, our Sunny 16 Rule Calculator offers a classic manual photography guideline.

Interpreting Long Exposure Results for Optimal Imagery

Professional landscape and architectural photographers don't just calculate long exposure times; they interpret the results with an understanding of various photographic nuances to achieve optimal imagery. When the calculator suggests an exposure time, they consider factors beyond simple light reduction. For instance, for multi-minute exposures, they anticipate reciprocity failure, a phenomenon where film and digital sensors become less sensitive to light over extended periods, often requiring them to add an extra 10-20% to the calculated time. They also factor in the dynamic ambient light changes (e.g., sunrise/sunset) that can occur over a long exposure, potentially requiring adjustments in real-time. Moreover, the desired intensity of motion blur dictates their final choice; a 0.5-second exposure might create a subtle flow in water, while 15 seconds produces a painterly mist. They look for specific shutter durations to match their artistic vision, ensuring the calculated number is a starting point, not an absolute.

Frequently Asked Questions

What is a long exposure in photography?

A long exposure in photography refers to using a slow shutter speed to capture light over an extended period, often several seconds, minutes, or even hours. This technique creates artistic effects like motion blur for moving subjects (e.g., silky water, streaking clouds) or light trails, while keeping stationary elements sharp. It's essential for low-light photography and achieving a minimalist aesthetic in landscapes. For example, an exposure of 0.5 seconds is considered long for capturing water movement.

How do ND filters work for long exposures?

Neutral Density (ND) filters are dark pieces of glass or resin placed in front of a camera lens to reduce the amount of light entering the sensor without affecting color. By decreasing light, they allow photographers to use much slower shutter speeds than would otherwise be possible in bright conditions. A 6-stop ND filter, for instance, reduces light by a factor of 64, turning a 1/125s exposure into a 0.5-second exposure. This enables the long exposure effects desired.

What is optical density in ND filters?

Optical density (OD) is a scientific measure of how much light an ND filter blocks, expressed as a logarithmic value. For example, an ND filter with an optical density of 0.3 blocks half the light (1 stop), while an OD of 1.8 blocks 6 stops (ND64). Higher optical density values correspond to darker filters and greater light reduction, which are necessary for achieving very long exposure times, especially in bright daylight. It's a precise way to quantify filter strength.