Guide to Solid ND Filters

Solid ND filters are an essential part of my landscape photography kit, yet I come across many photographers that do not use them. Put quite simply; ND filters are a dark piece of glass or resin that you put in front of your lens to let less light into the camera. What this achieves is a slower shutter speed without having to change your aperture.

What is wrong with stopping down your aperture to f/22 to achieve a slower shutter speed? Diffraction.

Diffraction is caused by light bending around an object. In this case, the small hole of the aperture at f/22. This bending of light causes softness of the image throughout the entire scene. To maintain image sharpness, you should not stop the aperture down past f/13 (f/9 on a crop sensor). Below is a crop of the same scene, f/8 on the left, and f/22 on the right. You can clearly see the loss of sharpness and lack of micro-contrast.

These ND filters should not be confused with graduated ND filters, graduated filters are dark on the top and gradually become clear at the bottom. A solid ND filter is completely dark and intended to change the exposure by letting in less light throughout the frame.

Solid ND filters come in a variety of darkness values and are labeled in different confusing terms. The most commonly used term is ‘Stops’.

This filter is often used when you need to slow down your shutter speed slightly. When shooting a scene with a river you may want to have texture in the water rather than a smoothed out cotton effect, to achieve this you need a shutter speed around 1/4 of a second. For example, if you were shooting at f/8 ISO 200 and your meter read 1/30s without a filter, putting on a 3 stop filter would give you the desired shutter speed of 1/4s. You could achieve the same shutter speed by stopping down to f/22 and avoid using the filter, but this would also increase the diffraction by using such a small aperture, causing your image to be soft. Using the 3 stop filter in this instance allows you to keep the sharpness of f/8 while getting a slower shutter speed.

This is the most useful filter for grand landscapes. When you use it during golden hour or at sunrise/sunset you will have an exposure anywhere from 30 seconds to 4 minutes. This will cause any moving clouds to blur and streak across the sky, showing interesting movement. The longer shutter speed also captures more colors due to the changing colors in the clouds.

When skies are brighter than sunset, like overcast conditions or just dense clouds, a 10 stop can be very useful. I would not start out buying this filter unless you have money to spare or know you want to do a lot of very long exposure photography. With a 3 and 6 stop you can stack to create 9 stops and then decide if the exposure times are long enough for what you want to achieve.

This is the filter you need for shooting in mid-day light when you want to streak the clouds, usually in black and white. A typical mid-day exposure is f/8, ISO 200, 1/800s, adding a 16 stop filter would extend the exposure to 1min 22s while maintaining sharpness at f/8. If an extremely long shutter speed is desired, you may add a 3 stop filter to achieve an 11-minute exposure. Adding a 6 stop would give you an 88-minute exposure (not recommended!)

Stacking multiple filters can be a great way to save money when more ND is needed. For example, you can stack the 10 and 6 stop filters together to achieve 16 stops rather than buying a 16 stop. When you do this, you need to be careful with wide-angle lenses to ensure this doesn't cause vignetting. To avoid this you should go up a size. For example, if your largest filter size on your lenses is 77mm, go up to 82mm to avoid vignetting when stacking.

These filters allow you to change the amount of ND with a simple twist, ranging from 2-8 stops. These are great in theory and can work well for many situations, but the reality is they only cover up to around 4-6 stops. When you go above that you will get banding where some areas are dark, and others are not. They also cause vignetting with ultra wide angle lenses. I would only recommend this filter if you do not shoot ultra wide, and only need 6 stops of ND. These can be great for waterfalls when you need to dial in a particular shutter speed. If you really want this flexibility on an ultra wide, get one that is bigger than your lens and use a step-down ring to avoid vignetting.

In an older version of this blog post I compared screw on filters and drop-in filters. Since then a new breed of ND filters have emerged, those are magnetic filters. After using these i cannot fathom going back to the old style filters. Therefore I will only be talking about the current magnetic ND filters.

Over the past couple years I have dabbled with different magnetic filters, primarily from Kase who were the innovators in this field. Since then, Breakthrough Photography and Maven have entered the market with their own magnetic systems. The key thing I have noted is that there has been little innovation since Kase released their original version. Yes, they now have color coded rings which is quite handy, but beyond that they are all the same.

That is until NiSi dropped their new system, and I'm impressed. The original systems had two major design flaws. The first being that they are hard to get apart, especially when using gloves. The second is that they tend to fall off your lens if you're not very careful. NiSi addressed both of these issues in a brilliant way by adding tabs to each filter to make them easy to pull apart, and adding an innovative locking system to ensure they will never fall off when used properly.

Because of these new features I now recommend the NiSi JetMag Pro Landscape ND Kit, which is available in our store to preorder.