I’m sure there’s been a moment where you’ve been left in awe after watching an image that has a soft and silky sky or river in it. Maybe you’ve learned that this is a technique that requires the use of a slow shutter speed but after some back and forth, your images look nothing like those you’ve seen.
That’s most likely because you’re not able to get a shutter speed much slower than one second.
The truth about this technique is that it requires the use of dark filter mounted in front of the camera’s lens. This is known as a Neutral Density Filter and it’s not without a reason that they’re considered essential by most landscape photographers.
Keep reading and you’ll learn why Neutral Density Filters will improve your photography and how you can quickly begin taking advantage of them.
What Are Neutral Density Filters?
A Neutral Density Filter, normally referred to as an ND Filter, is a darkened piece of glass that’s mounted to the lens in order to reduce the amount of light reaching the camera’s sensor. This means that it takes a longer time for an image to be correctly exposed, so the use of a slow shutter speed is required.
You can compare this with photographing in a dark room compared to a well lit one; the first requires a much longer shutter speed (or higher ISO) in order to collect as much detail as you’d get in a well-lit room.
Landscape photographers use this technique in order blur moving elements within the frame, such as the waterfall in the image below:
Let’s take the example of differently lit rooms and translate that into a more relevant situation for a landscape photographer where you’re photographing a waterfall and want to blur the water:
You might notice that a shutter speed of 1/500th of a second gives you a well-exposed image when photographing during the daytime. However, this is too quick to blur the water even the slightest; you’d need an exposure time of up to several seconds to do that.
Recommended Reading: Long Exposure Photography Without Filters
Using a narrow aperture, such as f/22, lets you slow down the shutter speed a little but the consequence is a loss of image quality. If it’s still bright outside, this little workaround won’t lengthen the exposure time enough to create a nice blur anyways.
The solution is a Neutral Density Filter.
Since the filter reduces the amount of light entering the camera, you’re forced to use a longer shutter speed. Exactly how long the shutter speed can be, depends on the filter you’re using; it could be anywhere from a second to several minutes.
The different types of Neutral Density Filters
It can be rather confusing to know what type of Neutral Density Filter to purchase if you haven’t looked much into them yet; there’s an abundance of brands, systems, setups and even types of filters.
To begin with, it’s important to understand that there are two main types of filter systems: Screw-In Filters and Square Filters.
Let’s take a closer look at each:
Alternative #1: Screw-In Filters
The first alternative is the round Screw-In filters that are, as the name indicates, screwed on to the front element of a lens. This type of filters is quite common and is typically the only option you’ll find in a general electronic store.
Screw-in filters are known to let less light slip through the mounting than square filters, which makes it easier to calculate the correct exposure. Personally, I don’t find this to be a big problem as I add this factor in the calculations for finding the correct shutter speed.
Another advantage of this system is that it takes less space and weighs a lot less. This may be an important factor for those who do longer hikes or prefer to have a lighter camera bag.
There are also downsides to the screw-in filter system, the major one being the difficulties of using multiple filters at once, known a stacking filters. Using multiple filters at once is quite common but when doing so with this filter system you’ll get an unwanted vignette around the photo. This is due to the outer edges of the filters being visible in the photo as you essentially extend the lens with a centimeter or two.
It’s not too difficult to remove the vignette in a photo editor such as Adobe Lightroom or Photoshop but, be aware, the more filters you use, the harder it gets!
Keep in mind that the filters aren’t expandable which means you might need to purchase different sizes for different lenses. Alternatively, you can purchase adapters but make sure that the filter is big enough to fit the lens with the widest diameter.
Alternative #2: Square Filters
The square filter system is slightly more advanced than the screw-in and requires a few extra pieces of equipment in order to be properly mounted to the camera.
Unlike the previous system where the filter is screwed directly onto the lens, an adapter is the first piece mounted with this square version. A filter holder is then clipped onto the adapter and it’s in here that you insert the filters.
The main advantage of using a square filter system is that it holds several slots where filters can be placed. In other words, it’s possible to use several filters at the same time without seeing any unwanted vignetting. Certain ultra-wide-angle lenses might get a slight vignette with some brands but it remains the same if you’re using one or three filters.
You’ll also find that this system is more flexible in use as you can rotate the filter holder and slide filters up and down in their slots in order to better align with the specific scene you’re photographing. This is especially important when using Graduated Neutral Density Filters.
Now, this system is bulkier than the screw-in filters and you’ll notice a significant difference in both size and weight. Though the higher quality options tend to be stronger, it’s also known that the square filters are slightly more fragile.
Keep in mind that there are big differences between brands both when it comes to the quality of filters and holders, and their design. For example, in the NiSi V6 Pro system, you can place a Circular Polarizer inside the filter holder but for other brands, you might need an additional adapter.
Most filter kits include adapters of different sizes but this might vary between brands. I recommend double-checking what’s included so that you’re sure you’ve got the correct adapter size for your lenses.
What’s the best system for Neutral Density Filters?
I’ll be honest with you right away: there’s no such thing as the perfect system for everyone. This highly depends on your preferences and budget. It took me years to find the system that’s perfect for me but my needs also changed during that period.
There are three main elements you should take into consideration when looking for the best Neutral Density Filter System: area of use, price and quality.
Area of use
The area of use is perhaps the most critical question when choosing between a screw-in or square filter system. If you’re someone who spends a lot of time hiking and already have a heavy backpack with limited space, screw-in filters might be the best fit. Those who don’t depend on saving weight are likely to appreciate the extra flexibility that the square filter system offers.
If you never stack filters and don’t intend to use Graduated Neutral Density Filters, the screw-in option is the better alternative. Adding the filter holder, adapter, pouches and filters seems a little overkill if you only use one Neutral Density Filter at the time.
However, if you do intend to use a Graduated Filter or perhaps a Polarizer and Neutral Density Filter at the same time, the square filter system is ideal.
The cost of purchasing a new filter and/or filter system varies drastically depending on the choice of brand, quality and system.
Square Filters are normally more expensive and you’ll also need a filter holder and adapters. This means the initial investment is considerably larger than if you were to purchase one or two screw-in filters.
That being said, filters from most manufacturers fit into the different filter holders so it is possible to choose a budget filter holder and higher quality filter (though I do recommend sticking to the same brand for both the holder and filters).
I find that a cheap alternative from any local electronic shop is the perfect place to begin. These are far from the best quality filters out there but they are good enough in the begin as you’re learning how to use them.
My first Neutral Density filter was a cheap screw-on filter found at a local electronic shop. The price was around $20. As a beginner photographer these where the perfect filters to begin with; they allowed me to use a slightly longer shutter speed but perhaps more importantly they helped me understand the relation between the essential camera settings.
I used these filters for a while before understanding that I needed a darker filter that could make it possible to achieve an even slower shutter speed. This was before square filters had become as popular as today so I ended up purchasing B+W screw-in filters.
These were a lot more expensive but the quality was also better. However, the B+W filters were at that time known for their strong red color cast, which I honestly didn’t mind at the time. Having a darker filter and reaching shutter speeds of up to a few minutes made it worth it.
It took me about one year until I switched to a square filter system as I wanted to use Graduated Neutral Density Filters too. I tried out both affordable and more expensive alternatives but quickly found that the cheapest are much more unreliable; either the holder breaks easily or the filters aren’t secured enough in it.
For the past years, I’ve stuck to using various systems from NiSi Filters. I’ve been extremely happy with these and am glad to have found a high-quality filter system with no color cast.
Understanding the degrees of darkening
Unfortunately, there aren’t good filters that fit each and all situation. As mentioned previously, the cheapest Neutral Density Filters only add a slight darkening, not nearly enough to properly smooth out the water. For this you need a darker filter and these tend to have a less welcoming price-tag.
Understanding the difference between the darkening of filters can get a little complicated. Perhaps you’ve already heard about the terms 1 Stop, 6 Stop and 10 Stop? These are the most common terms to use when talking about the degrees of darkening.
Simply put, the terms tell you how much less light reaches the sensor when placing the filter in front of the lens and, consequently, how many stops you need to extend the shutter speed with.
For example, a 1 Stop ND Filter reduces the amount of light with 1 Stop and requires you to extend the shutter speed with the same. In other words, you can double the exposure time.
The much darker 10 Stop ND Filter allows you to extend the exposure time by 1000. That means what would’ve been a 1/125 second exposure without the filter now needs to be 8 seconds. This is when you can properly blur the water and stretch the clouds.
In addition to the terms 6 Stop or 10 Stop, you might also see a classification such as ND1.8 or ND3.0. This is another method of explaining the darkness of the filter but, for now, stick with understanding the stops. This can quickly get confusing!
These are the most common grades of Neutral Density Filters:
- ND0.3 or 1 stop = 2x shutter speed
- ND0.6 or 2 stops = 4x shutter speed
- ND0.9 or 3 stops = 8x shutter speed
- ND1.8 or 6 stops = 64x shutter speed
- ND3.0 or 10 stops = 1000x shutter speed
There are even darker filters, such as the 16 Stop, that can be used to create minute-long exposures even during broad daylight.
How to Use Neutral Density Filters
So how exactly can you use Neutral Density Filters to improve your photography? Is it as simple as just mounting one to the camera and start getting good results?
Yes and no…
Let’s take a closer look at a few examples so you can understand the different effects that’s possible to achieve by using these filters.
Example #1: ‘Quick’ Long Exposure
The first type of image we’ll look at is one that requires the use of a ‘lighter’ Neutral Density Filter such as a 1,2 or 3 Stop. These aren’t going to result in extreme long shutter speeds where the water looks like milk and the clouds are stretched across the sky. Instead, you’ll start seeing some motion blur while still keeping texture.
Exactly how long of a shutter speed you can use depends on the light you’re shooting in. If it’s in broad daylight the difference is minimal while early morning or late evening you might reach a shutter speed of a few seconds.
Remember, a 3 Stop ND Filter requires a shutter speed that is 8 times longer than the original no-filter image.
Take the image above as an example. The shutter speed was 1/5th of a second but due to being close to the very quickly moving water, it was just enough to create some blur in it. Without using the 3 Stop ND Filter, there wouldn’t have been any motion in the water at all.
The clouds, however, still remain frozen. This is because they’re not moving quickly enough to create a blur with this quick of a shutter speed. For that to happen, you need to use a darker filter.
Example #2: ‘Semi-Long’ Long Exposure
The next example we’ll look at is when the filters are used to create a long exposure where the elements begin to get the ‘frozen’ or ‘milky’ effect we talked about in the beginning of the article. Typically, a 6-Stop ND Filter works good for this purpose when you’re photographing during the golden hours or in dimmed light.
In the image below I used a shutter speed of 20 seconds. This has successfully blurred the ocean and you start noticing a slight blur in the clouds too.
Without the filter the water would still be choppy and the clouds would have no motion blur at all. Here’s almost the same shot but without using filters to get a slow shutter speed:
Example #3: Ultra Long Exposure
In the final example, we’ll look at a scenario where the shutter speed is so slow that the water looks like ice or glass and the clouds are stretched across the sky. This is the result of a 120 seconds exposure time and a 10 Stop ND Filter.
Capturing images with such a slow shutter speed requires some more planning and a few more steps than normal. For example, I highly recommend taking one or two test shots before mounting the filter so you know roughly what shutter speed you need to get a good exposure.
With time you’ll learn to roughly estimate the ideal shutter speed based on the chosen filter and how bright it is outside. In the beginning though, using an app such as NDCalc helps you get the best results.
There are several other factors involved in capturing these images too and I recommend reading out Ultimate Guide to Long Exposure Photography for an in-depth introduction on the subject.
In my opinion, there’s no doubt that using Neutral Density Filters will improve your photography. That’s exactly what it did for me. Now, it’s not going to improve your photography in the sense that your images turn world-class overnight but it’s going to give you a much better understanding on how the fundamental settings work.
You’ll learn exactly how much of an impact the shutter speed has and you’ll learn how to take advantage of this to create interesting and impactful images.
There’s an abundance of filters available on the market and there’s no doubt that it’s a significant investment if you want to get the best quality filters. While I do recommend a high-quality filter setup at some point, a cheap option is just as good of a place to start. Just make sure that you get a few filters with different degrees of darkening so that you’ve got something for different scenarios.
It’s not without a reason that these filters are considered essential among most landscape photographers. There are few types of gear that can have such a big impact on the final image.