Not sure what a neutral density filter is? Can't figure out how to use one? Then this article is for you...
Though using neutral density filters might be a more advanced topic than you're used to, with a little guidance, there's no reason why a beginner photographer can't use ND filters and use them well.
In this guide, you'll learn what an ND filter is, the different types of ND filters and their purposes, and how to use one to create more dramatic photos as well.
Let's get started!
What is an ND Filter, and What is It Used For?
Think of an ND filter as sunglasses for your camera's lens. A neutral density filter is designed to block a certain amount of light from entering the camera's lens, just like sunglasses are designed to block light from entering your eyes.
The purpose of doing so is to be able to use slower shutter speeds during the day to get beautiful motion effects like you see above.
If you tried to take the same shot using the same camera settings in broad daylight without an ND filter in place, you'd end up with a photo that is way too bright, or overexposed.
What's more, using ND filters also allows you to use very large apertures, which limits the depth of field.
Doing so keeps the subject in sharp focus, but the background is nicely blurred, as shown above.
Again, if you used a large aperture like f/1.4 in broad daylight you'd need a lightning-fast shutter speed to prevent overexposure - sometimes a shutter speed so fast that your camera can't accommodate.
However, with an ND filter in place, you can use that huge aperture and a much slower shutter speed as well to avoid that problem and get the nicely blurred background you want.
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What are the Different Types of ND Filters?
ND filters are classified using their light-stopping power. That is, the darker the filter is, the more light it will absorb.
So, an ND filter with 0.1 light-blocking power is a much lighter filter than one with 0.9 light-blocking power.
Common designations for ND filters run the gamut from 0.1-0.9. Some companies, like Marumi, offer even darker ND Filters, like 1.2 or 1.5.
It's important to note that these numbers refer to the optical density of the filter. But sometimes ND filters are referred to by the number of f-stops you can reduce when using the filter.
The more f-stops the filter reduces, the less light that enters the camera's lens. That means that a 2-stop ND filter blocks twice the light as a 1-stop ND filter. A 4-stop ND filter blocks twice the light as a 2-stop ND filter, and so on.
Confusingly, some ND filters are described as being ND4 or ND8 and so forth. What does that mean?
It's just another way to specify the darkness of the filter. In this case, ND2 means a 1-stop filter because it allows 50% light transmittance, which is measured as 21 (2x1 = 2) An ND4 filter, which allows 25% light transmittance, is measured as 22 (2x2 = 4). An ND8 filter, which allows 12.5% light transmittance, is measured as 23 (2x2x2 = 8). You get the idea...
The whole point here is that the darker the filter, the more light that's blocked and the longer your shutter speed can be. Therefore, regardless of whether a filter is labeled as 1.5, 5-stop, or ND32, you know that it's darker than an ND filter labeled as 0.6, 2-stop, or ND4.
Rather than try to figure out all that math on your own, there's an app for that.
In fact, there are a number of long exposure apps you can use, but my particular favorite is LExp - Long Exposure Calcs.
This easy-to-use app will tell you how long or short your shutter speed should be based on the filter you're using. It even has specific calculators for things like shooting landscapes, the stars, and fireworks.
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Which ND Filter is Right for You?
The ND filter you use really depends on the look you want in your final image.
If you want very slight indicated movement, a lighter ND filter like an ND4 is in order. Conversely, if you want very strong movement effects, go for something like an ND32 filter. For even more pronounced effects, you can go super dark with an ND500, like the one shown above.
Really, this all comes down to experimentation. If you find that you can't achieve the motion blur you want with a lighter filter, try a darker one and see what results you get.
As a rule of thumb, though, 0.6 (2-stop), 0.9 (3-stop) and 1.2 (4-stop) filters are a good place to start for long exposure landscape photography.
Whatever kind of ND filter you get, they're easy to use.
In the case of the Marumi filters referenced above, they simply screw onto the end of the lens. Once attached, use the LExp app to help you determine the right camera settings and fire away!
Final Thoughts
Using ND filters can, at first, be a little confusing.
However, my hope is that with these quick tips, you'll find that you better understand what ND filters are, how they can benefit your photos, and their value as an important piece of your photography kit.
So, grab yourself a couple of ND filters, find some clouds, moving water, or passing cars, and see what beautiful creations you can make with an ND filter!