Some photos are beautiful enough to look like blended paintings and can rack in plenty of comments when you post them on your Instagram. However, finding ways to blur or blend the background without using special effects in photoshop can be tricky. One way that photographers can create unique effects without having to do any editing afterward is with ND filters.

Even if you aren’t completely sure what this tool is, chances are that you’ve seen the technique in action before with landscape photography. Here’s an in-depth guide that covers everything you should know about an ND filter, ND filter charts, and editing in post.

The Purpose of ND Filters 

Neutral density filters, or ND filters, are like a pair of sunglasses for your camera. Just as you would wear sunglasses to block out the light in a bright room, an ND tool blocks the light as it comes towards your device. There is one difference. While sunglasses can tint the light you see or make it appear darker, an ND tool won’t change the color of the light it blocks. 

If you’ve never used neutral density filters before in photography or in post-editing, the concept might sound a little odd. After all, letting your camera capture light is supposed to be a positive thing, right?

Most of the time, letting your device soak up the light is great, but blocking the light with a neutral density filter can create an interesting effect. 

To get as much of the sun as you need, the ND tool forces you to open the shutter up and expose the device to light for a longer amount of time. While it doesn’t work with every subject, ND filters can add a certain amount of style to your image, especially with landscape photography. 

man holding filter in front of field

Photo by SplitShire Licensed Under CC0

What Can You Achieve with ND Filters?

When you use them correctly, there’s a couple of things that ND filters can do to improve the overall “look” of your pictures—one has to do with your shutter speed and the other deals with aperture. 

Aperture

Most people would probably argue that the more sun they have to work with, the better off they are. However, there are a couple of exceptions when it comes to aperture. If you’ve ever tried shooting with a wide-open aperture in the middle of a sunny day, you already know how overexposed your images can get.

An ND tool can help avoid this issue. With the right lighting and aperture, you’ll get selective focus effects as well as a shallow depth of field in those bright environments when shooting photography.

Shutter Speed

A little bit more common way to use or post-filters has to do with your shutter speed. Since you’ll have less of the sun entering the camera to help with the exposure, you’ll also need to slow down your shutter speed as well.

Slowing it down means that a lot of the subjects in your shot, especially objects that move, will blur. Even slow-moving objects, like a cloud in the sky, can blur and blend into the background with a slower shutter affecting the exposure. 

What Do the Numbers on ND Filters  Represent?

ND filters come in all shapes and sizes, or different darkness levels and strengths. As convenient as it would be to have an ND tool that just tells you how many stops of light it will darken the correct exposure, it usually doesn’t work like that.

Instead, you’ll have either an optical density number or an ND filter factor number to work with. Both the optical density and the filter numbers are helpful, but neither of them directly tells you how much they’ll reduce the sun. 

You can use an filter chart to help pinpoint exactly how much less sun you’ll have, according to the optical density number on the chart and the tool. There are plenty of different filter charts already online, which can you use if you’re trying to figure out the stops of light on a tool you want to buy or one that you already own. 

There is a quick calculation you can use to make the process a little easier. You’ll need to cut the amount of light entering your camera “in half” for every stop of the ND tool.

Once you’ve done that, you’ll need to double your shutter speed if you want to maintain the same amount of correct exposure. If you add another ND stop, you’ll need to double your shutter speed again. 

Let’s Look at Some Practical Examples

Without using ND filters in real-time, the explanation of how shutter speed and exposure works can be a little confusing. Here’s a practical example to make things a little clearer.

Imagine that you’re shooting waterfall photography, and you’re looking to use an ND tool so that you can blur the waterfall. If you’re shooting in the middle of the day, even an f/16 lens would still end up freezing the water. 

However, let’s say that you’ve got a six-stop ND tool with you, and you place it on your lens. Your original exposure without the ND would be an f/16 and a 1/800 shutter speed. 

With your 6-stop tool, your new exposure would be around 1/13. The difference there is notable—instead of freezing the water and bringing it into focus, the ND tool would “soften” the waterfall and let it blur into the background. 

ND Filters Can be Stacked

One technique that a lot of people who work with filters like to use is “stacking.” There’s no reason you have to limit yourself to only one tool, and if you do have more than one, you can use multiple films on the same shot. 

There isn’t any complicated math to do, either. For instance, if you’ve got that six-stop tool we’ve talked about before and you combine it with a four-stop tool, you now have a ten-stop filter at your disposal. 

There is a disadvantage to the stacking technique. The more filters you add on, the more barriers that the light has to pass through to get to the camera and lens.

This can make it tricky to control which elements blur or refract light in your shot, so you have to be careful with how many filters you stack. It can mess with your exposure, and prevent you from getting a shot that has balanced exposure in it. 

ND Filters Come in Different Shapes

Not all ND photography filters look the same, but many of them are circular, and easily screw onto your camera lens without much effort. A larger camera lens might use drop-in filters, but it depends on the camera.

While it is uncommon, some of these filters are rectangular or even square-shaped and require special holders to screw onto your lens. The good news is that, regardless of shape, the filter rating system is the same. 

Different Types of ND Filters

Here are a few different types of ND photography tools that you should be on the lookout for. We’ve included a brief breakdown below in the article, but we’ll go into more detail about each individual type later on. The kind you need can depend on the amount of exposure in your picture. 

  • Variable Neutral Density Filters (VND) – A VND tool is convenient if you like to use a different amount of stops. Instead of carrying around multiple filters that you might need to stack, the variable neutral density filters will allow you to adjust the rating filter with the outer ring. Depending on the specific VND that you buy, your tool might allow you to change from 2-stops to 8-stops. The only potential downside that new users might experience with a VND is a cross-pattern. If you place the filters on the maximum setting, you could get a cross-pattern on your picture. 
  • Graduated Neutral Density Filters (GND) – If you’re interested in experimenting with darkness and light levels when it comes to the exposure, the graduated neutral density filters might be the right choice for you. With this tool, you can change the transition area from dark to light or vice versa. If you have an image with uneven exposure, such as a bright background with a dark foreground, a GND can help you balance it out. Sunset or sunrise pictures might require the use of a GND. 
  • Polarizing Filter – You might not know it, but it’s possible that you already own a polarizing ND filter. If you’re trying to cut down on potential sun glare, a polarizing tool might be able to help you correct the mistake during the editing process. 
  • Center Neutral Density Filters (CND) – As probably the most uncommon type of density tool, a CND has a dark center with lighter edges that helps balance the exposure of images with uneven sun exposure.

ND Filter Shapes and Sizes

We’ve briefly talked about the different types and shapes of ND filters in this article, but if you’re serious about purchasing one, it’s important to know the pros and cons of these filters. Here’s what you should note: 

ND Filters can Screw-on Direct to Your Lens

The screw-on type, which is usually circular in shape, screws right onto your camera lens. These tools tend to be inexpensive, and fairly common for photographers that don’t use ND tools on a regular basis, or who are just looking to try them out. 

Pros

  • Inexpensive – Some of them only cost around $10 to $15
  • Variety – There are plenty of brands to pick from
  • Versatile – While they can work for different subjects, these screw-on tools look great with a long exposure landscape shot.

Cons

  • Not always high-quality – Depending on the brand you pick, your tool might not be durable or have enough strength for what you need

ND Filters Accessory Holders

Although they can be a little less common across the board or in landscape photography, an ND tool that requires a special holder to attach to your device is another option. If you want to identify this type of filter immediately, you’ll notice that they usually aren’t circular. 

Pros

  • Better quality – For landscape photographers that want a filter that will last them much longer, an ND filter with a holder might be the way to go. They tend to be much higher quality. 
  • Versatile – You can use these tools with a wide variety of different lenses. 

Cons

  • More expensive – Better quality comes at a price, and it’s usually much higher than a screw-on filter. You might also need to invest in an adapter ring to fit the filter onto your lens. 

How They Are Used in Solar Photography

If you’re interested in solar photography or even trying to capture a shot of a solar eclipse, some filters might be able to help you with the exposure. While it can vary based on the specific brand, a lot of manufacturers will state that heavy-duty tools with sixteen stops or more are suitable for solar photography and exposure.

Keep in mind that, before heading out to shoot a solar eclipse, you should always make sure the specific brand you’re using clarifies that it’s okay, and you shouldn’t use an optical viewfinder.

Viewing filters that photographers typically use for photography can block out harmful UV radiation, but average ND filters cannot. You’ll want to make sure you use a live mode or electronic viewfinder.

Graduated ND Filters

We’ve already talked a little about the basics of a graduated neutral density filter in regards to your photography needs, or GND, but now we should go into a little more detail. A GND tool can help balance out the sun in your scene, and it can make it easier for you to shoot at different points during the day without worrying about overexposure. 

Many landscape photographers feel as if they can only shoot during the “golden hour” of the day since the light will be soft. With a graduated neutral density tool, you don’t need to limit yourself anymore. 

GNDs are usually rectangular, and they contain a piece of glass or resin that has a gradient that goes from dark to light. This is what helps the circular object balance out the picture once you screw it or fix it onto your device.

Although it contains a gradient, people still consider these “neutral density” tools since the dark part of the object doesn’t make any color differences or color casts in your picture. There is a chance you might get a cross-pattern or slight color difference with some cheaper tools, but if you stick to well-established brands, that shouldn’t be an issue. 

Graduated neutral density tools work well at specific points of the day, especially sunset or sunrise. They can help you nail the exposure and prevent your foreground from being dark with an overexposed sky or background.

Some professionals might argue that editing their photography images in post or using Photoshop in post is just as effective as a filter, but it all depends on what you’re trying to do. The GND can save you a few minutes in the post-editing process as well as prevent you from losing details in the final image.

If there isn’t a substantial difference between the light in the foreground and background of your picture, you might not need to use a graduated density tool at all. Some people tend to use a GND only if there’s at least a two-stop difference in the light of their image. 

There are Different Strengths Associated with ND Filters

We’ve covered GNDs, but there’s still more detail to go into about the different strengths of a neutral density tool. Since you measure a filter in stops, you always have to consider the amount of light you’re using.

An eight-stop tool is cutting the light by eight stops in a row. If you aren’t sure how much strength you need from your tool, it’s okay to start small.

Before you jump to a 10-stop tool, you might want to consider using a 2-stop or 4-stop one first and seeing if you like the result. Keep in mind that you should really only focus on changing the shutter speed on those long exposure landscape shots. The more “strength” you use, the more you’re likely to get a picture with a blended background and blurred objects. 

Varied Numbers for ND Stops

When you look at the filter chart, you’ll see different numbers for stops. This can be confusing, especially since the manufacturer doesn’t always make it clear how many stops a tool has.

Instead of saying that your ND tool has 2-stops, they might say it has an “optical density of 0.6” or even an “ND factor 4.” Trying to convert these numbers into ND stops is where many people get into trouble or waste minutes figuring it out.

If you’re trying to use a chart to figure out what you might need, don’t be afraid of any confusing numbers. The “optical density number” and “ND factor” tell you how many stops your tool has, they just do it in a different way. The best thing you can do is focus on how many stops the tool has rather than any other numbers that might pop up.

ND Filters: Which Ones Are Considered Best? 

While it can depend, there are a few simple guidelines you can follow when picking out how many stops you want from your ND tool. It’s worth it to note, but for long exposure shots that blur the clouds in the sky or blend a waterfall, you should consider a tool that’s at least six-stops but maybe even up to ten-stops. Your exposure times will be up to four minutes, but at least thirty seconds. 

If you’re trying to shoot an object in motion, such as a man on a bike ride, you won’t need something that’s quite so heavy-duty for your exposure times.

A two-stop or four-stop tool can do the trick for your exposure times. Objects that are constantly on the move don’t need long exposure times, and using a ten-stop choice for your exposure time might only mess up your shot or leave you with hours of editing in post. 

Equipment You Could Potentially Need With ND Filters

canon camera

Photo by Free-Photos Licensed Under CC0

You might think the only thing you need is a camera and your ND tool, but there’s a little more equipment that can go into creating the long exposure shots that so many people love.

One of the essential pieces of equipment you’ll need is a tripod. You might be able to hold your device still for a few seconds, but it’s almost impossible to hold a large device still for multiple minutes without shaking. Shaking usually isn’t an issue you can fix in post. 

If you plan on using a six-stop ND tool or anything more, having a tripod to support your device during the shot is crucial.

A cable release or remote trigger can also come in handy on occasion, and you can use them in conjunction with a setting on your device called “bulb mode.” 

If you’re new to ND tools, you might want to stick away from variable neutral density tools, or VNDs. They can look appealing since they allow you to adjust the strength of the filter, but it’s also easy to get lines and cross-patterns across your image too. Before trying a VND, it might be easy to stick with a few different two-stop or six-stop ND options first. 

What Brands You Should Consider When Looking to Buy

If you’re curious about where you can get an ND tool from, you have plenty of options to pick from regardless of your type of photography. Four notable manufacturers to check out are Lee, HiTech, Nisi, and Cokin.

Dedicated people might be able to find something high-quality and durable at Lee or HiTech, but if you need a budget option, Cokin is a better place to start with photography. 

Ultimately, picking the right brand comes down to your individual photography needs. The type of filter you choose can often depend on the type of device you have, how often you plan to use the object, and how many stops you’re looking for. 

Is There a Best Time To Use ND Filters?

sunset over mountains

Photo by kareni Licensed Under CC0

Some people might be curious about when the best time to use an ND tool might be. As convenient and easy as these objects are, they aren’t perfect for every picture, so you have to be selective about when you choose to use them.

For instance, many people like to use ND tools to make water appear smooth like glass. The tool can blend some of the water’s distortion together and make it appear much smoother than it actually is.

However, trying to accomplish this with ocean waves or even a rough sea can be almost impossible. Unless you’re dealing with water that’s already fairly calm, this isn’t the best place to use an ND filter. 

Using an ND tool on an overcast day or a mostly sunny day with only a few clouds can be an appropriate point. The clouds might add a little texture, but they can contrast well against a soft, smooth sky.

Sunrise and sunset photography, which many people refer to as “the golden hour” are usually one of the best points to pull out your filter and device. Since the light is at its softest, you shouldn’t have too many issues with overexposure. 

Around midday or noon, when the sun is at its brightest, an ND tool might be difficult to use. On a sunny day, the light is often too bright for a long exposure shot. If you have a GND, you might be able to deal with some of this overexposure, but it’s not a guarantee. 

Carrying a Physical Copy of the Filter Chart

There is some controversy when it comes to whether or not you should carry a physical copy of the chart with you on photography outings. While some professionals recommend that you do, others argue that smartphone apps can bring up a chart or calculate exposure for you without as much hassle. 

There is a downside to relying on a smartphone. If you don’t have great service or you run out of battery power, you’ll be stuck. For people that might hike mountains or trek through snow and freezing conditions for the perfect shot, these are real concerns. 

This is where it can be helpful to have a physical copy of a chart with you. All you need to do is print out a copy of the chart, fold it up, and stick it in your bag.

How to Correctly Use a Filter Chart

Although charts can be great reference tools, they can still be tricky to understand and use in real life if you don’t have tons of experience with them.

To use the chart, the first thing you want to do is set your device up in the desired position and get it ready to take the picture you want. You’ll also want to adjust the exposure time till it’s in the right place without using a filter. It’s important to look at the shutter speed, and keep your shutter speed in mind. 

Next, you should look at the chart and find your shutter speed in the left-hand column. This is a quick note, when checking your shutter speed but make sure that the filter ND chart you’re using corresponds to the correct ND filter you have for your cameras.

For instance, if you’re using a two-stop filter, you don’t want to look at a chart for ten-stop filters if you’re trying to work with landscape photography.

Once you’ve found the shutter speed, you can input the new shutter speed into the device that you plan to control your camera with during bulb mode. If you’re using a cable release button or remote trigger, you’ll just need to adjust it to the right shutter speed. 

If your time falls below thirty seconds, you might not even need to put your device in bulb mode or fiddle with a remote trigger. Even if something doesn’t end up looking right, you can always work on it in post. If you don’t think it’s blended enough, a little editing in post could help fix the problem. 

While an ND filter isn’t for every type of picture, they can add a bit of flair or style to a landscape photo and their photography. As long as you understand how to use the chart and which ND filter you might want to work with, you can begin capturing blended and smooth landscape shots to post on your social media accounts (or just to enjoy).