Light is the key ingredient in photography and whereas studio photographers are in complete control of the light sources they use, those of us who shoot landscapes have no direct control. We are at the mercy of the weather, and this can make it a frustrating business. What we can do, however, is to apply a certain amount of control as to how, and how much light enters the lens, or even which part of it. For many years, this has been achieved through the use of filtration, which enables photographers to reduce the extremes of contrast in harsh lighting conditions, cut out reflections and saturate colours, artificially extend shutter speeds and alter colour balance.
When digital photography really started taking off, there was speculation that this would spell the end for filter manufacturers, as so many filtration effects were replicable in post-processing. However, the fact is that more filters are being sold than ever before, to the extent that one major producer was struggling to meet demand for some time.
So why are filters still selling in such large numbers? Well, simply because they still do some things which can’t easily be achieved in software – the main exception being warm up and cool down filters, whose job can now be done with greater ease and precision by adjusting white balance. And when it comes to effects which can be replicated on the computer, it’s often easier and quicker to do it in camera with filtration.
Ice Beach, Jokulsarlon, Iceland
There are some effects which can only be achieved using in-camera filtration. For this picture, I wanted to catch the movement of a wave drawing back around the ice and needed an exposure time of several seconds. In the prevailing lighting conditions, this wasn’t possible, even at base ISO with the lens stopped down to minimum aperture. To achieve the necessary exposure time, I fitted a 4-stop neutral density filter and a polariser. The polariser had the added benefit of reducing glare, helping the ice to stand out from the background. Canon 5D mark III, 16-35mm f/2.8L at 18mm, ISO 200, 4 seconds at f/16, a 4-stop ND, polariser.
Not all filters are created equal
It’s important to mention first and foremost that not all filters are created equal. In regard to filters, you truly do get what you pay for. Lower priced filters can cause color casting, providing you with unnatural and unwanted color to your images. For example, some filter companies are notoriously known for there being a magenta tint to the images. The best advice we can give you is to do your research. B+W Filters sets a high standard for high-quality optical glass. They were also the first filter manufacturer to incorporate water and dirt repelling MRC multi-layer and scratch-resistant coating to their filters which comes in handy for those of us who are hard on their gear.
Filters are available in two types – screw-in and slot in. Screw-in filters are round and screw directly onto the lens’ filter thread. Slot-in filters are square or rectangular and they are held in position with a dedicated filter holder, which is attached via an adaptor ring screwed onto the lens. The advantages of a slot-in system are that they make it easier to use filters in combination, and in the case of graduated filters, they can be positioned to align precisely with the horizon. For these reasons, slot-in systems are generally recommended over screw-in filters.
Companies such as B+W Filters offer both Slot-in (also called Drop-In) filters as well as screw-on filters.
There are basically three different types of filter which digital landscape photographers will find useful: graduated neutral density filters (GNDs or ‘grads’), full neutral density filters (NDs) and polarizing filters.
Graduated Neutral Density Filters
One of the most common lighting problems in landscape photography is that the sky is much brighter than the land, and the range of contrast from the brightest tones to the darkest is beyond the camera’s dynamic range – the range of tones it is capable of capturing. What typically happens in this situation is that the camera will either expose the sky correctly, but underexpose the foreground, or it will expose the foreground correctly and overexpose the sky.
To solve this problem, many photographers use graduated filters, which have a neutral grey half and a clear half, with a transition zone where the two meet. Simply place the grey half over the bright sky to balance the contrast in the scene and bring it within the dynamic range of the sensor. Grads come in different strengths – typically one, two and three stops – to allow for different levels of contrast.
For this picture, I needed a 3-stop grad to prevent the brighter tones in the sky from overexposing, and selected a soft-edged one so that the transition line wouldn’t obviously cut into the building.
They also come in ‘hard’ and ‘soft-edged’ varieties, which refers to how sudden the transition is from the dark to clear half. Hard-edged grads are most useful when the horizon is fairly level, but with an uneven horizon, a soft-edged grad may be a better bet, as the transition line of a hard-edged grad may be obvious. That said, with smaller formats (up to ‘full frame’ 35mm digital) this is rarely a major issue, as the transition line even of hard-edged grads is spread over a relatively large percentage of the recording surface.
In the ideal world, you would have a set of both hard and soft-edged filters, but if you are on a budget and can only stretch to one or the other, I’d recommend getting a set of hard-edged grads, as these will be useful in a wider range of situations.
There is also a third type of GND – the ‘reverse’ grad, which has a darker strip on the transition line, and then gradually fades away towards the top of the filter. While they do produce slightly better results than standard grads in some situations, they are far from essential, and there are techniques, both in-camera and in software, which will help you deal effectively with the situations in which you might find yourself reaching for a reverse grad. You can, for example, put a second grad upside-down in the filter holder, to create a darker strip in the middle of the frame.
GNDs are not difficult filters to use, but there a couple of points you need to bear in mind. The most common mistakes are using a filter of the wrong strength (the tendency being to over-grad scenes) and not positioning it correctly. Remember that most of the time we expect the sky to be brighter than the land, and it will look unnatural if it is too dark – the exception being a front-lit subject under a stormy sky. Therefore, you should generally aim to leave the sky 1 stop brighter than the land, although this also comes down to personal taste.
When deciding which strength grad you need, take a spot meter reading from a mid-tone in the foreground and a reading from a bright (but not the very brightest) part of the sky. Then, do the calculation and choose a filter that will best suit the scene. Absolute accuracy is less critical with digital than when shooting film, as minor adjustments can be made in processing. As a rule it’s better to err on the side of leaving the sky a little too bright – as long as you don’t blow any highlights – and darken the sky in processing. This works better than having to lighten an overly dark sky, which can reveal noise and artefacts.
Lining grads up accurately is a skill which comes with practice. If you don’t pull the filter down far enough, there will be a light band on the horizon, with a darker sky above it – if you pull it down too low, you’ll see the transition line cutting into the foreground. Check the review image and look specifically for these problems. When trying to position your grads, try wiggling them up and down a little in holder – this will help you to identify where the transition line is. Modern cameras have Live View features. Switch on Live View, set the camera to manual and adjust the exposure for the foreground. Now, start pushing the filter up and down in the filter holder, it will be much easier to see the gradation line while you are moving the filter.
Of course, the big question remains: in the digital age, just how necessary are graduated neutral density filters? Well, with the increased dynamic range of modern sensors and software techniques such as HDR (blending various exposures), you may find that you need to use grads less than in the past, but they certainly still have their uses.
Firstly, even though current cameras are capable of recording a very wide range of tones, there are still plenty of scenes which will fall outside their dynamic range. And although you can add graduated filter effects during processing, if the camera hasn’t recorded the information in the first place, then software won’t be able to help you. Secondly, although HDR and manual exposure blending are viable alternatives to using in-camera filtration, there are a couple of disadvantages. The most obvious one is that you need to spend more time on processing, which for many people may not be an issue, but when you are trying to process a large number of images and a deadline is looming, every second counts.
The other problem is caused by moving elements and changing light. If something moves significantly from one frame to the next, it can cause problems when trying to merge images. And if the light changes between captures – which is a real possibility during longer exposures – then the sky and foreground may not look natural when blended together.
There are occasions though, when grads won’t do the job, and it becomes necessary to bracket exposures and blend them on the computer. For example, in situations when the difference in brightness is too extreme for filters to have sufficient effect or when the horizon is so uneven that even a soft-edged grad becomes obvious. This is usually when there is a large object such as a building, breaking the horizon.
In my experience, manual blending usually gives more natural results: take one shot exposed for the sky, another for the land and open them up in Photoshop. Layer one shot on top of the other, create a layer mask and then gradually paint away the top layer using a soft-edged brush, slowly revealing the layer below.
There are some situations where grads won’t work, and it becomes necessary to bracket images and blend them in software. In this instance, the shape of the cliff made it impossible to position a grad without it being obvious that filtration was being used, so I exposed one capture for the sky with a shutter speed of 2 seconds, and then another for the foreground and cliffs with a shutter speed of 15 seconds. The two shots were then blended manually using layer masks in Photoshop.
Neutral Density Filters
ND filters have a neutral grey coating over their entire surface and they are designed to absorb light, reducing the amount which enters the lens and reaches the sensor. This allows photographers to use longer shutter speeds than would be possible without filtration, to creatively blur moving elements in the landscape such as water or clouds. They are produced in a wide range of densities, from 1 stop to 10 or more stops.
With lower density filters up to 3 or 4 stops, unless you are shooting in very low light conditions, you should be able to rely on your cameras through the lens metering. With more extreme ND filters, however, there will often not be enough light coming through the lens for your camera to be able to meter accurately. In these situations, take a test exposure without the filter, and then double the exposure time for every stop of filtration you add. For example, if the unfiltered exposure is 1/60 second and you want to shoot with a 10-stop ND, you will need an exposure time of 16 seconds. Switch to manual mode and set the shutter speed to the desired value. If you need to expose for more than 30 seconds, put the camera in Bulb mode and lock the shutter open with a shutter release cable for the required time. Don’t forget to adjust the aperture (in Bulb mode) to the aperture you used to take the test exposure.
ND filters are extremely popular with landscape photographers as the longer exposure can completely alter the look and feel of a picture, creating in many instances, an ethereal atmosphere. At the moment, there is no real alternative to using ND filters; the effect cannot be recreated successfully in software and very few cameras have an ISO setting lower than 50. Camera makers have always seemed intent on pushing high ISO limits, but there is only so far they can go; perhaps the next step will be to work on low limits, which could, in time remove the necessity for ND filters.
You can’t really reproduce the effects of long exposures in software, this is something you need to do in-camera, and unless the lighting conditions are exactly as you want them, you will need to use neutral density filters to reduce the amount of light falling on the camera’s sensor. For this picture I wanted to smooth out the surface of the water, but I didn’t want an exposure length which would cause the clouds to streak excessively. A four-stop ND enabled me to push the exposure from 0.8 second to 15 seconds.
Light which reflects off non-metallic surfaces such as glass, water and leaves scatters and creates glare which reduces contrast and colour saturation. By only allowing through light which is vibrating in a specific plane, polarising filters reduce this glare and restore the natural colour saturation and contrast present in a scene. They are perhaps best-known for boosting the colour of blue skies, but work well in a variety of situations and can work especially well in woodland scenes by removing the glare from wet leaves.
The effect is strongest when the filter is at a 90º angle from the light source and by rotating the filter the effect can be increased or decreased. They are relatively simple to use, as you just look through the viewfinder and rotate the filter until you see the effect you want. There are a couple of points to be aware of, though. The effect of polarising filters can be very seductive, and it’s easy to over-polarise a scene, to the extent to which blue skies appear almost black – remember, you don’t have to always set the filter to maximum polarisation. Also, with wide angle lenses, the effects of polarisation can be uneven, causing a banding effect in blue skies, although this will depend on the cloud formations. If you are taking a series of pictures to stitch together into a panoramic, then avoid the use of a polariser, as the degree of polarisation will change as the camera rotates and the angle to the sun changes.
There are two types of polariser – linear and circular. This doesn’t refer to the physical shape of the filter, but rather to the way they polarise light. Linear polarisers generally have a stronger effect, but can interfere with modern autofocus and metering systems, so the usual advice is to choose a circular polariser. However, if you focus manually, and check exposures with the camera’s histogram, there is no reason why you shouldn’t be able to use a linear polariser.
Polarizers are another filter whose effects are impossible to successfully replicate digitally, so if you haven’t already done so, make room for one in your camera bag.
Boosting Colour and Contrast
If you want to reduce glare in a scene and restore natural colour saturation, you will need to do it when you take the picture, using a polariser. At first glance the effects might seem subtle in this comparison, but there is a lot more ‘punch’ in the sky of the polarised picture, together with a clearer reflection and better contrast overall.
Photography has changed dramatically over the last ten or fifteen years, with digital technology maturing, and sophisticated post-processing techniques becoming widely accepted. However, there are still benefits to doing some things the old-fashioned way, and in some cases, these tried and tested techniques are the only way of achieving the results that you want.