Filters are one of my most used pieces of photography equipment; it’s rare that I take a shot without one. If you’ve not used them before, they are basically pieces of glass that attach to the front of your lens that help to achieve a variety of different effects. The following are three types of filters that are of most interest to a landscape photographer.
1. Neutral Density (ND) Filter
Neutral density filters are dark pieces of glass that reduce the amount of light entering the lens. Think of them as sunglasses for your camera. They come in a range of "strengths" which determines how much light they shut out. Why might this be helpful? For landscape photography, it allows you to decrease your shutter speed so that you can manipulate the rendering of motion in a photograph.
2. Graduated Neutral Density (GND) Filter
Often referred to simply as a “grad,” graduated filters are similar ND filters but instead of being evenly dark, there is a graduation between dark to light. One side of the filter is clear, blocking out no light. The opposite side is dark, but the darkness tapers off towards the center of the filter. A grad is used to control uneven light in a scene, most typically reducing the brightness of the sky to provide better balance with the much darker land. Grads also come in a variety of strengths describing how dark they are in the darkest portion of the filter.
3. Polarizing Filter
If you’ve ever worn a pair of polarizing sunglasses, you’re familiar with what this filter can do. More simply referred to as a polarizer, it has the effect of reducing glare from reflective surfaces, most commonly water. This helps to be able to control the extent of reflections at its most effective, allowing the camera to “see through” the water. By cutting the reflected blue-white light of the sky, it also helps to create richer, more saturated colours. It has the same effect on the sky by cutting out the blue-white light bouncing around to create a darker, bluer sky that helps to define cloud formations sitting on the sky’s bluer canvas.
But, Do I Need Filters?
It’s often said that in a world of digital photography filters are redundant. While I strongly disagree, it’s something to consider. Here’s how you may filter your photographs in post-processing.
The grad is most often used to balance a bright sky with a darker land. This is particularly problematic at sunrise and sunset when shooting towards the sun. The grad will darken the sky such that you can increase the overall exposure of the photograph so that the land isn’t quite so dark.
With digital photography, you can use a technique called “exposure blending” to overcome the same problem. The basic approach is to take two (or more) photographs—one with a well-exposed sky and one with well-exposed land—and then blend the best bits of each image to create the final image.
This result is the same as using the graduated filter. Blending’s major advantage is that you can darken the sky even if the horizon is an irregular shape (e.g., when photographing trees or mountains). In contrast, a graduated filter has a straight transition that results in objects above the transition point being artificially and undesirably darkened. In these situations, blending results in a more natural effect.
A series of 3 bracketed shots to be blended together -2EV (left), 0EV (center), +2EV (right). The sky from the first two images is used to replace the burned out sky in the third image, which has a much better exposure for the land.
The resulting image of the 3-exposure blend.
Further, the much-improved dynamic range of modern cameras makes it possible to capture a single image without grad while retaining highlight and shadow detail, adjusting the relative brightness of the photograph in Lightroom to suit.
Nonetheless, I personally prefer to use grads most of the time. Exposure blending requires multiple shots to be taken which take up more space on the hard drive, makes organization in Lightroom slightly trickier, but most of all it causes problems if there is any motion in the image where objects do not align in both frames.
For the beginner, I think exposure blending (or even HDR) can be both daunting and tempting. Yet I find the constraint and cruder control of grads help to develop a greater appreciation of the tones in an image and the quality of light. It is easy to go off the path with exposure blending to create an image that looks artificial. Using grads and developing a visual awareness of what looks right makes it easier to make considered use of more advanced techniques such as exposure blending.
There are techniques available that recreate the effect of ND filters in Photoshop. The basic approach is to take many photographs such that the cumulative exposure time of all of the photographs matches your intended shutter speed. You then merge these frames in Photoshop, which averages out the motion in a similar way to a longer shutter speed.
That is far too much effort, HD storage, and clutter in Lightroom for my liking, especially as I shoot a lot of longer exposures. I would much rather get it right in a single frame using an ND filter.
I personally don’t believe there’s any way to effectively recreate the effect of a polarizer in post-processing. Mimicking the extra contrast and saturation, perhaps, but I’ve found that removing that white-blue glare to reveal the remaining colours, texture and details, the sheen on wet rocks, the slightly washed-out look that shooting without a polarizer can bring is impossible to pull off in the digital darkroom. Nik’s Color Efex 2 software has a polarizing filter that helps a bit, but in no way replaces the real thing. Regardless, it’s just more work (a lot more work!) for something that can be easily done in the field.
Left: Unpolarized shot. All of the rocks were wet from a rainy day (taken from under an umbrella). Notice the significant glare on the central rock, which I had envisioned as the hero of the photograph.
Right: Polarized version. The glare on the central rock and the water to the left has been removed, bringing back the brilliant colours I had experienced at the time.
Of greater importance is the effect filters have on your visualization. It’s true that some effects can be recreated in post-processing, but it can leave a gap in your creative process when in the field. I’m not aiming to get my final image out of camera as I will always do some post-processing, but I do want a good approximation of what the image might look like to inform my creative decisions. Is the shutter speed too long or too short? That line in the water is interesting; what can I do to strengthen it? The textures revealed in those rocks are really beautiful; how do the other elements in the frame complement them? That line in the cloud almost mimics the shape of that rock; should I move to emphasize that further?
If these questions and decisions are left entirely to the digital darkroom, your creative process has been stunted and opportunities missed. For the sake of carrying a few extra pieces of glass, the benefits in terms of following the creative muse are huge.
What Strength NDs Do I Need?
This is a big question; it depends on what you photograph and your aesthetic preferences. There’s no blanket answer, and the light, weather conditions, time of day, and camera settings have a strong influence on filter choices.
Generally, I recommend a 3-stop and a 6-stop ND. My 3-stop is my most used filter, usually blocking enough light to add some smoothing to water in shaded gorges and around sunrise/sunset. The 6-stop further opens my shooting window, allowing me to use longer exposures before sunset than would be possible with the 3-stop. When shooting an hour or two before sunset, I start with the 6-stop, switch to the 3-stop as the light drops and sunset approaches, and then remove it altogether when the twilight of “blue hour” is low enough that no filtration is needed for longer exposures. This way I can shoot longer exposures in good light for several hours, maintain some consistency (if I was so interested) in shutter speeds by reducing my filtration over time, and modulate my camera settings (lowering or raising ISO, opening or closing the aperture) to bridge the 3-stop gap between the two filters.
If you wanted to shoot long exposures during the middle of the day, then you’d need to look at 10- or 16-stop filters. As a mostly golden/blue hour photographer, these are a bit niche for me, so my 10-stop gets little use.
For graduated NDs, I tend to use a 2-stop grad with a hard transition. Hard refers to how sudden the graduation in the filter is, with soft being more gradual and less obvious and hard being more abrupt (and so more troublesome with trees and mountains as noted above). A 3-stop filter may be more beneficial if you find yourself shooting into the sun, where even 3 stops might be insufficient and you may need to stack filters (e.g., a 2- and 3-stop). In this situation, I generally prefer to exposure blend to avoid excessive flare, the extra strong transition from the 5 stops of filtration, and the top of the frame where the filtration is strongest tends to get too dark.
Without the benefit of a 3-stop ND filter, it would have been difficult to see the effect of the white water in the bottom right corner such that I could re-recreate it in post-processing. It’s a key compositional element which would have been missed without a filter.
What Should I Get?
There are many different brands and filter systems on the market, and with the explosion in interest in compact system cameras (aka APS-C/m43 mirrorless), manufacturers have developed scaled-down filter systems to better suit the size and portability of those cameras.
In terms of system, you have the choice of using circular screw-in filters or a filter holder that attaches to an adapter ring on your lens into which you slide in square filters. Filter holder systems tend to be the most popular and versatile; they clip onto an adapter ring which screws onto the front of your lens like a normal screw-in filter and provides 2 or 3 slots into which you slide square filters. I leave my adapter rings attached to my lenses so that I can set my filters up very quickly simply by clipping on the holder, rather than having to screw anything on.
When stacking (using multiple filters at once), you can replace them by just sliding one out and replacing it. Being larger than the lens diameter, they are also less prone to vignetting than screw-in filters when stacking. A major benefit is that graduated filters can be repositioned to suit the scene by sliding it up and down in the filter holder. By contrast, screw-in filters have the transition across the middle of the filter, condemning you to a life of photographs with the horizon in the middle of the frame.
If used in isolation, screw-in ND filters do have advantages. They don’t suffer light leaks like filter holders sometimes can, whereby the light can enter the lens via the sides of the holder causing strange optical effects in the photograph.
I would avoid cheap filters at all costs; they are made from cheap materials, resulting in strange colour casts and loss of image quality. It may be more expensive but look at it as an investment by buying a good quality brand such as Lee, Singh-Ray, B&W. I have recently switched to using Formatt-Hitech’s Firecrest filters and they are very colour neutral.
Experiment with filters and have fun. Your landscape photography will benefit from it!
Interested in more than just a point-and-shoot landscape experience? Duncan's eBook, The Perfect Shutter, explores how the creative use of shutter speed can impact your landscape photography in a beautiful way.
Duncan Fawkes' passion for photography developed as an upwelling of suppressed creativity stemming from his background in corporate IT management. With a love and respect for nature and the outdoors, he hopes that his photography shares the world as he finds it, in its many moods and forms. He readily admits that being alone in the natural environment is where his senses come back to life, awakening from the slumber of modern living. Duncan is a strong advocate of being true to your inner creative, believing that art is about self-expression rather than pretty pictures to hang on walls or trophy locations to bag.
A native of Scotland, Duncan now lives in the idyllic surf town of Yamba on the northern NSW coast of Australia, where he runs photographic workshops not only in Yamba but also further afield, taking people to places off the photographic route to provide a clean slate for students to find their own interest and reaction in the landscape. Learn more about Duncan on his website and his Facebook page.