What Is an ND Filter and How They Can Improve Your Photos

Have you ever wondered how photographers capture silky smooth waterfalls?

Or how they smooth out the water in seascapes?

One of the secrets is a Neutral Density (ND) filter.

Yellow hut, Lofoten Islands, Norway, shot with a 10-stop ND filter
ND filters can help smooth out water in seascapes. Yellow hut, Lofoten Islands, Norway, shot using a 10-stop ND filter. Photo by Verity E. Milligan.

In this article, we will explore what is an ND filter is and how to use it in your long exposure photography.

What Is an ND Filter?

An ND filter is a solid, dark plate of glass or plastic that is often square in shape and fits into a filter holder which attaches to the front of your lens.

You can also purchase circular, or screw-in versions, which attach directly to your lens.

The idea behind an ND filter is to reduce the amount of light coming into the lens, which allows you to expose for longer shutter speeds.

This also allows you to capture a scene with a long exposure.

An ND filter attached to a DSLR camera lens
ND filters come in different shapes and sizes. Their basic functionality is to reduce the amount of light reaching the sensor.

The length of the exposure will be dependent on factors such as the time of day, shutter speed, and aperture.

These longer exposures can range from a few tenths of a minute to many minutes, depending on the strength of the filter you’re using and the time of day.

Hamnoy, Lofoten Islands, Norway, shot with a 10-stop ND filter
A 10-stop ND filter was used in this shot of Hamnoy, Lofoten Islands, Norway. Photo by Verity E. Milligan.

You can buy ND filters of various strengths, the most popular is a 10-stop (or x1000), which reduces the amount of light reaching the sensor by 10 whole stops. 

When and Where to Use an ND Filter

Neutral Density filters come in very handy for particular types of photography; such as landscapes, waterfalls, seascapes, or even street photography.

Uttakleiv Beach sunrise, shot with a 10-stop ND filter
This image of Uttakleiv Beach, Lofoten Islands, Norway, was shot with a 10-stop ND filter. Photo by Verity E. Milligan

Extending the exposure time when photographing movements accentuate the impression of movement, which adds artistic flair to an image.

For example, longer exposures give water a milky quality, which adds a misty, almost dream-like, quality to a shot.

Padley Gorge, Peak District, shot with a 6-stop ND filter
A long exposure and a 6-stop ND filter was used here to photograph Padley Gorge, Peak District. Photo by Verity E. Milligan.

ND filters are also great for creating movement in the sky. For example, a 15-30 second exposure can give the impression of clouds moving.

ND filter image of clouds moving over Gandan, Ulaanbaatar, Mongolia
ND filters can help you create the impression of clouds moving. Photo of Gandan, Ulaanbaatar, Mongolia, by Tsolmon Naidandorj on Unsplash

This can be particularly effective if you’re shooting architecture photography in an urban environment.

ND filters can also add impact to street photography or busy cityscapes. If there are many people or lots of traffic in a shot, an ND filter combined with a long exposure can reduce their appearance and create an artistic ghosting effect in their place.

Edinburgh at night, shot with a 6-stop ND filter
A long exposure has created a ghosting effect on some of the cars in this shot of Edinburgh at night, using a 6-stop ND filter. Photo by Verity E. Milligan.

There is no right or wrong scenario when using ND filters. If you’re feeling creative, you can indulge in some ICM (Intentional Camera Movement).

What is a Neutral Density Grad Filter?

Our eyes are incredibly versatile. We can look at a sunset and perceive the entire range of light. For example, You can see the brightest points of the sky, yet still, perceive the detail in the shadows.

Unfortunately, this skill does not transfer to our cameras.

This is where a Neutral Density graduated (ND Grad) filter comes in handy.

The ND Grad is designed to maintain detail in the sky by darkening it, while also allowing you to expose for the foreground.

A soft vs. hard nd grad filter illustrated
A hard edge ND grad filter (left) has a more pronounced transition from dark to light areas, whereas a soft edge ND grad (right) has a smoother transition.

This means you can avoid those pesky instances where either the sky is too bright or the foreground too dark. 

Gas Street Basin, Birmingham, shot with a 0.9 soft ND grad filter
A 0.9 soft ND grad filter was used here to capture Gas Street Basin, Birmingham. Photo by Verity E. Milligan.

Different Types of ND Grad Filters

ND grad filters come in different varieties and strengths. You can get soft or hard versions, which relate to the line between the darkened section and the rest of the filter.

Hamnøy Harbour sunset, Lofoten Islands, Norway
Canon 5D Mk IV + 16-35mm III @ 16mm Lee Filters Circular Polariser + Little Stopper (6-Stop ND). f/10, 30 second exposure. Hamnøy Harbour, Lofoten Islands, Norway. Photo by Verity E. Milligan.

The hard version has a very definitive line so you would need a subject with an obvious horizon–such as a seascape–to get the best results.

There are also various strengths in terms of how dark the filter is at the top.

These come in 0.3, 0.6 and 0.9 strengths; which equates to a 1, 2 or 3 stop reduction in light entering the lens (through the dark edge).

Wast Water sunset, Lake District
Sunset over Wast Water in the Lake District. taken with Canon 5D Mk IV + 16-35mm III @ 16mm. Lee Filters Circular Polariser + 0.9 ND Grad. f/14, 3.2 second exposure. Photo by Verity E. Milligan.

The thing to remember with ND grad filters is to make sure you’re using the clear area of the filter to expose for the darker areas of the image, or your results will be less than desirable.

What to Look for When Purchasing an ND Filter

When you invest in a filter, you can either go for a singular screw-in filter that attaches directly to your lens or one that slots into the filter holder that sits on the front of your camera lens.

A screw-in filter attached to a DSLR lens
A screw-in filter that directly attaches to the DSLR lens.
A square ND filter attached to the front of a DSLR lens
A square filter that slots into a filter holder on the front of your lens.

a screw-in filter might be cheaper and easier to transport, but the latter is more versatile. Using a filter holder means you can use the ND filter in conjunction with other filters.

If you’re purchasing a square filter you’ll need to invest in a filter holder. This can bump up the cost, especially as you’ll need a filter adaptor ring for your lens–but it is worth the money.

The bonus of using a filter holder and an adaptor ring is you will be able to use the filter on any lens, regardless of its diameter. This works out much cheaper than purchasing a new filter for every lens you have.

Selfridges, Birmingham, shot with a 10-stop ND filter
A long-exposure photograph of the exterior of Selfridges department store in Birmingham, shot using a 10-stop ND filter. Photo by Verity E. Milligan.

There are many varieties of ND filter on the market to cater to all costs and needs. The premium quality filters will cost more than the cheaper alternatives.

Naturally, the higher the quality of the filter, the better the image quality. Cheap plastic filters are great for beginners though, especially if you are not used to using filters. However, there can be a downside, such as strange color casts or noise. I would recommend investing in a mid-range set, so you don’t get frustrated with the color cast issue.

Horgabost Beach storm, Isle of Harris, shot with a 3-stop ND filer
A 3-stop ND filter was used to shoot this storm over Horgabost Beach, Isle of Harris. Photo by Verity E. Milligan.

5 Best ND Filters

Here is a list of my top 5 ND filter recommendations.

1. Lee Filters 100x100mm Big Stopper

This is probably the best-known 10-stop filter on the market, known for its precision engineering and high-quality glass. This is a great addition to any landscape photographer’s kit bag.

Lee Filters 100x100mm Big Stopper

2. Lee Filters 100mm Little Stopper

This is the Big Stopper’s little brother. This equates to 6-stops, which is great for sunsets or sunrises when you wish to capture long exposures but don’t want to be waiting for long stretches of time.

Lee Filters 100mm Little Stopper

Lee Filters 100mm Little Stopper

3. Kase Filters 100mm Wolverine ND8

Kase are the new kids on the block, but have some really nice filters. This is the equivalent to 3-stops, which is good for seascapes when you just want a hint of motion rather than a longer exposure.

Kase Filters 100mm Wolverine ND8
Kase Filters 100mm Wolverine ND8

4. B+W XS-Pro Digital ND Vario MRC-Nano Filter

If you don’t want to purchase a filter holder and associated kit, B+W have a screw-in ND filter which can vary from 1 to 5 stops. The downside is you’d have to buy a different one for each of your lens sizes.

B+W XS-Pro Digital ND Vario MRC-Nano Filter
B+W XS-Pro Digital ND Vario MRC-Nano Filter

5. Lee Filters Neutral Density Soft Edge Grad 0.9

This is the perfect filter to balance out exposure if you’re dealing with variable light. It can be used in conjunction with other ND filters.

Lee Filters Neutral Density Soft Edge Grad 0.9
Lee Filters Neutral Density Soft Edge Grad 0.9

Over to You

So if you’re looking to capture eye-catching seascape, waterfall or street photography, add an ND filter to your kit bag. It could help take your photography to the next level.

What Is An ND Filter
What Is An ND Filter And How They Can Improve Your Photos

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