A few months ago I added a set of neutral density filters to my kit bag. My only regret is that I didn’t start using them earlier. Neutral density filters or ND filters are glass or resin filters that reduce the speed at which light passes through the filter element and in turn enters the camera lens. Neutral density filters vary in strength from a reduction of 0.3 stops to a much as 15 stops. They are ‘neutral’ in that they do not alter the colour or spectrum of the light passing through. They come in a number of styles, ranging from screw on filters attaching to the front of a lens to resin or glass plates which can be stacked in front of the lens using a custom mount.
So what do you use ND filters for? They have a number of creative uses, but I mainly use them for controlling the evenness of an exposure and for increasing the length of time which I am able to keep the camera shutter open for. Think in terms of shooting a seascape. You are often confronted with a bright sky and a dark ocean. If you meter off the sky, the camera underexposes and you lose the tones in the ocean. If you meter the ocean, the camera overexposes and the sky blows out. The result is an image which is never balanced. Using ND filters allows you to creatively control or ‘reduce’ the exposure in an area susceptible to highlight blowouts such as the sky.
There are two types of ND filters; graduated ND filters and full or ‘stopper’ ND filters. Graduated ND filters transition from a dark tint to a normal tint across the face of the filter. Graduated ND filters are most useful in reducing areas susceptible to highlight blowouts. Graduated ND filters usually have a reduction rating of 0.3 stops to 1.5 stops. They usually also vary between soft, medium and hard transitions.
A Lee 0.6 graduated neutral density filter was used in combination with a Lee 'Little Stopper' ND filter to produce this image. The 0.6 graduated filter allowed the clouds to be exposed correctly, giving extra punch to the top half of the image.The camera was set to 30 seconds, f/18, ISO 100.
Full or ‘stopper’ ND filters are a uniform tint and they reduce the exposure of the image across the entire face of the filter. The reduction rating can vary from 6 stops to as much as 15 stops. This allows the user to use a longer exposure than what would normally be permitted. This in turn can have the wonderful effect of ghosting movement. For landscape photographers, this is ideal for making people and traffic disappear and giving water a lovely, misty appearance. The benefits of ND filters is that they can also be stacked allowing you use a stopper filter in combination with a graduated filter to reduce bright skylines and areas subject to highlight blowouts while also increasing the length of time for which the shutter can remain open.
Captured using a Lee 'Big Stopper' 10 stop ND filter. The 10 stop ND filter allowed the camera to be set to 125 seconds, f/18, ISO 100.
Using ND filters is easy. Graduated ND filters by themselves can simply be gauged straight through the lens. Simply put the filter in place, look through the lens or viewfinder and decide which parts of the image you wish to darken. Stopper ND filters need an exposure calculation as they are not transparent to the naked eye. This is usually the reciprocal of the stopping power of the ND filter. For example, a six stop ND filter needs an exposure six stops lower than the meter reading on the camera without the filter in place. So, a shutter speed of 1/60 metered in normal conditions needs to be compensated to 1 second in order to produce a good exposure. Fortunately, there are dozens of apps which can do this calculation for you and they are readily available for download to a smart phone or similar device. From experience, it does help to know the fundamentals for those dreaded occasions when your trusty smartphone is not at hand.
In terms of brands, I enjoy using Lee Filters. But I have heard equally good reports about NiSi. I would recommend staying away from the cheaper brands. Nothing is worse than putting a cheap filter in front of an expensive lens and camera. To start out, I would recommend kitting yourself with at least one stopper ND filter and combination of graduated ND filters. I prefer ND graduated filters but you can get warming and cooling tints to add extra colour to skies and sunsets. In most cases, you will also need an adapter set to suit your camera setup. Throw in a polarising filter and you won’t have much change left over as good quality ND filters are expensive. Of course, with long exposure times, a sturdy tripod is a must as is a cable or remote shutter release.
Brisbane City & Story Bridge
Another example of an image shot in combination with a Lee 'Big Stopper' ND filter and a 0.6 graduated ND filter. The graduated ND filter reduced the exposure of the sky by 0.6 stops to even out the image. The Big Stopper ND filter allowed a very long exposure to be used, removing the river and pedestrian traffic and giving the water a lovely glass like appearance.
As a word of caution, ND filters are not supposed to alter the colour of the light passing through. The reality is that even best quality filters tend to produce a slight blue tint. This is great you shoot in black and white but some correction is required if you prefer colour. Set your white balance to a warmer tint or be prepared to do some extra post processing after your shoot.
ND filters have improved my landscape photography tenfold and opened a broad range of creative possibilities. Don’t make the same mistake I did. If you are serious about your photography, start using ND filters. You won’t regret it.