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In an earlier article, I wrote that neutral density filters are the secret weapon of the landscape photographer. I couldn’t work without mine and I suspect most landscape photographers would say the same.
But why are they so useful? There are two reasons. One is that neutral density filters give you control over exposure, and the other is that they give you creative control over shutter speed.
Let’s take a closer look at these concepts.
First, some definitions. A neutral density filter is one that blocks light. The result is that less light passes through the lens and reaches the camera’s sensor (or film).
There are several ways of measuring the strength of neutral density filters, but they are basically all different ways of stating how many stops of light the filter blocks. Typical strengths are one stop (0.3 or ND2), two stops (0.6 or ND4), three stops (0.9 or ND8), six stops (1.8 or ND64 )and ten stops (3.0 or ND1024). Some manufacturers even make neutral density filters that block 16 stops or more light, although these are more of a specialty item.
This photo shows a ten stop neutral density filter mounted on a lens. As you can see the filter is nearly opaque and you can’t see through it well.
Neutral density filters block light evenly across the frame. Graduated neutral density filters, on the other hand, block light across just part of the frame. Half the filter is clear, and half is opaque, with a graduated area in-between (hence the name).
This photo shows a two stop Lee graduated neutral density filter in a square filter holder. The top half of the filter is dark (to block light) and the bottom is clear.
Graduated neutral density filters (often just called grads or GND filters) are used by landscape photographers to control exposure.
Imagine you are taking a landscape photo that includes the sky and the setting sun. In this scenario, the sky is much brighter than the foreground. If you expose correctly for the sky, the foreground goes dark. If expose correctly for the foreground, the sky is burnt out.
A graduated neutral density filter blocks light from the sky without affecting the foreground. If for example, the sky is three stops darker than the foreground then a three-stop graduated neutral density filter will help even out the difference between the two, allowing you to capture the scene in a single frame.
For this first photo below I set the exposure by exposing to the right (on the histogram) so that there were no clipped highlights. The problem is that the bottom half of the photo is too dark. You can make it lighter in Lightroom, but not without introducing noise.
I made another photo (below) and increased the exposure by two stops. The foreground is exposed properly but now the sky is burnt out. There is no way to bring back the lost highlight detail in Lightroom.
I made this last photo using a three-stop soft graduated neutral density filter. The filter allowed me to capture detail in both foreground and sky.
The advantage of using the filter is that it let me continue working as the light faded, taking longer exposures without having to bracket. The last photo of the evening had an exposure time of six minutes.
It also saves time in post-processing compared to using techniques like exposure blending or HDR in Lightroom. Before digital cameras (and processing), graduated neutral density filters were the only way that photographers had to balance out exposure between foreground and sky.
Graduated neutral density filters do have some disadvantages.
The first is that they don’t work well with scenes broken by something that sticks up above the horizon (like a tree or mountain).
The photo below is a good example. The sky is a small part of the frame and it’s impossible to cover it with a graduated neutral density filter without making the rocks darker as well. The only solution was to take two different exposures, one for the foreground, the other for the sky, and blend them in post-processing.
Another disadvantage is that good quality graduated filters are expensive.
Despite this, some landscape photographers like to use them as it gives them choice. With graduated neutral density filters you can decide which technique is best suited for the scene you are photographing.
Landscape photographers use neutral density filters for creative control over shutter speed.
Think about the exposure settings landscape photographers tend to use. You normally set ISO to the lowest setting and aperture to f/11 or f/16. This gives you maximum image quality (low ISO) and good depth-of-field (narrow aperture).
The shutter speed required to give the correct exposure will depend on the ambient light leves. In bright light, it might be around 1/125th of a second. In the fading light at the end of the day, it might be around 1/2 second.
But what if you want a longer shutter speed? This is where neutral density filters come in. They block light so that you can get longer shutter speeds. Longer exposures allow moving parts of the landscape (like clouds or water) to blur, which in turn creates mood and atmosphere.
The ultimate example of this is long exposure photography, where exposures of several minutes are used to blur the motion of the sea and clouds. Here’s an example. This photo was taken at ISO 200, at f/11 for 1/125th of a second.
With a neutral density filter, I was able to turn that into a shutter speed (exposure time) of 210 seconds. The photo is transformed.
One of the problems with neutral density filters is that there are so many to choose from. How do you know which ones to buy? Ultimately you have to decide how much you want to spend and then look at the options. But I can start by telling you which filters I own, why I bought them, and give you some tips for choosing filters.
But before I do that, I’d like to make the point that filters are very closely related to lens size. The bigger your lens, the bigger the filter required to cover the front element, and the more expensive it will be to buy. The difference can soon add up to hundreds of dollars. You have to bear in mind the filters you may want to buy later when you buy the lens itself.
My neutral density filter kit is the circular Formatt Hitech 72mm Firecrest Joel Tjintjelaar Signature Edition Long Exposure Kit #1. It contains three neutral density filters with strengths of three, six and ten stops respectively. You can also use two filters together to block nine, 13 or 16 stops of light. I bought the circular filters because they are less expensive than the square ones. (NOTE: if you plan to use your filters on multiple lenses, buy the size you need for the largest one, and get step-down rings to adapt the filters to fit the smaller ones – OR get the square drop-in kind instead.)
My graduated neutral density filter kit is the Lee Seven5 system, which I bought in a set that includes the filter holder, an adapter ring, and four graduated neutral density filters. The Lee Seven5 system is smaller (and less expensive) than Lee’s full size filters and is designed for mirrorless camera systems. This comes back to the point I made earlier about lens size.
I love these filters because they help me take photos like this.
I would love to hear from you what neutral density filters you use. Which ones did you choose and why did you buy them? What brands would you recommend to other photographers? Please let us know in the comments below.
If you enjoyed this article and would like to learn more about landscape photography then please check out my ebook The Black & White Landscape.