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How to Choose the Right ND Filter for Long-Exposure Effects

How to choose the right ND filter

Long-exposure photography has quickly become one of my favorite styles, which is evident when looking through the images I’ve captured over the last few years. More and more of my images use a shutter speed slower than half a second, and I take fewer handheld shots.

One reason I’ve become such a big fan of long-exposure photography is that it opens many creative doors. You’re less limited in your work and have endless options for how you want your image to look. You can use ultra-long shutter speeds for ethereal skies and silky water, or you can use more moderate shutter speeds to create blur while maintaining texture.

However, this benefit also presents a challenge: How do you choose the right shutter speed for long-exposure photography? And, since achieving long-exposure shutter speeds almost always requires a neutral density filter, which ND filter should you use?

I don’t believe there’s one correct shutter speed or filter for long-exposure photography. A big part of the creative process is to follow your preferences and aim for the look you want to achieve. However, to achieve the desired look, it’s crucial to understand how different ND filters affect your image.

In this article, I explore how three common ND filters (3-stop, 6-stop, and 10-stop) impact your images and the scenarios where each is most beneficial. By the time you finish reading, you’ll know how to match the neutral density filter to your creative vision!

Let’s dive right in.

Which neutral density filter should you use?

Choosing the Correct ND Filter for Long Exposure Photography Effects

Neutral density filters are designed for one simple purpose: they block light from entering the lens, allowing you to lengthen your shutter speed (or widen your aperture) beyond what the light levels normally allow.

For instance, when shooting in bright light at ISO 100, you might need an aperture of f/8 and a shutter speed of 1/1000s to capture a well-exposed image. If your goal is to capture a long-exposure shot, you’ll need to block a lot of light to drop your shutter speed to the requisite level – and that’s where an ND filter comes in handy.

Since ND filters come in different strengths, long-exposure photographers generally carry a few in their camera bags. Then, depending on the look they’re hoping to achieve and the light, they pick the perfect filter and capture the image.

Of course, this is easier said than done. Predicting the effects of an ND filter takes an understanding of its strength, combined with an understanding of moving subjects and how they’re affected by different shutter speeds. Let’s take a look at the most popular ND filter strengths and what you can expect from them:

3-stop ND filter

If you’re even loosely familiar with neutral density filters, you may know that a 3-stop filter won’t have a huge impact during brighter hours. Compared to the 6-stop and 10-stop filters, the 3-stop is not particularly dark and won’t allow for extremely slow shutter speeds of several minutes. Remember that three stops of light is fairly small; it’s the difference between 1/800s and 1/100s.

That said, the 3-stop ND filter remains one of my favorites. I particularly enjoy using it when photographing waves from a low perspective.

Choosing the Correct ND Filter for Long Exposure Photography Effects

The picture above was taken a couple of hours after sunrise, and due to the sun’s low position in the Arctic sky, it wasn’t daytime-bright. Without a filter, the shutter speed would have been too quick to capture the motion I wanted in the water. But slapping a 3-stop ND filter over my lens allowed me to lengthen the exposure time to 1/3s, which was just enough to capture the motion in the rushing waves and achieve the look I wanted. As you can see, the waves aren’t silky smooth – there’s still some texture and a sense of energy and motion – but they’re not completely frozen, either!

Had I used a 6-stop ND filter instead, the image would look quite different, as the longer shutter speed would have blurred the water and caused me to lose the texture I was aiming for.

Basically, the 3-stop filter is good for those situations where you’re dealing with relatively dim light, and you want to slow down the shutter speed in order to gain a bit of motion blur without getting that ultra-long-exposure look.

6-stop ND filter

A 6-stop ND filter might sound only a little stronger than a 3-stop ND filter, but the name is misleading. You see, a 6-stop ND filter lets you lengthen the exposure time by six stops. In other words, it’ll block eight times as much light compared to a 3-stop ND filter.

As a result, if you’re already using a relatively slow shutter speed due to the sun’s low position, you can achieve a very slow shutter speed with this filter.

Choosing the Correct ND Filter for Long Exposure Photography Effects

For the image above, I used a 6-stop ND filter to blur the water and create a softer feel. The filter allowed me to extend the exposure time to 15 seconds, which was enough to blur the water and create motion in the sky.

Look carefully at my sunset shot, and you’ll notice that the iceberg in the foreground actually started to blur with a 15-second shutter speed. Had I used a 10-stop ND filter and an exposure time of a few minutes, all the ice would have been blurry due to constant movement. On the other hand, a 3-stop ND filter wouldn’t have slowed the shutter speed enough to blur the water and achieve the desired look.

10-stop ND filter

The 10-stop ND filter is perhaps the most popular filter for those new to long-exposure photography. The effect is highly visible, and the images created with it can grab attention immediately. Though darker filters are available (such as 16-stop and 20-stop models), the 10-stop filter is often associated with long-exposure photography.

If you use a 10-stop filter in bright light, you can drop your shutter speed to around a second or longer (depending on the intensity of the light and your other exposure settings). This comes in handy for those daytime shots where you want to capture some nice motion blur (or where you want to render certain moving subjects, such as pedestrians, mostly invisible). Use a 10-stop ND filter in relatively weak light, and you’ll be able to lengthen your shutter speed from fractions of a second to minutes.

Choosing the Correct ND Filter for Long Exposure Photography Effects

The image above is a typical example of how a 10-stop ND filter can create a surreal look. With the filter in front of my lens, I used a shutter speed of four minutes to blur the lake and achieve a soft, dramatic look in the sky as the clouds were dragged out.

While it requires more planning and patience than the other two filters, the 10-stop filter has the biggest visual impact straight out of the camera.

Capture beautiful photos with an ND filter!

Choosing the Correct ND Filter for Long Exposure Photography Effects

As I mentioned earlier, there’s no single correct filter. Instead, you should understand how different filters affect your image and choose the one that brings you closest to your envisioned result. If you want a bit of motion blur and you’re already working in dim light, a weaker ND filter, such as a 3-stop model, is often the way to go. On the other hand, if you want a lot of motion blur, or if you’re shooting in bright light and require some motion blur, a 10-stop ND filter is the better choice.

Long-exposure photography opens many creative doors and provides several new elements to work with. A big part of this technique involves trial and error, but as you continue learning, you’ll begin to see what you need to capture the images you want!

Now over to you:

Do you have a favorite ND filter? What do you think about different ND filter effects? Share your thoughts in the comments below!

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Christian Hoiberg
Christian Hoiberg

is a full-time landscape photographer based in the scenic Lofoten Islands who helps aspiring photographers develop the skills needed to capture beautiful and impactful images. Visit his website to get a free download of his eBook 30 Tips to Improve Your Landscape Photography.

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