Getting the best from a polariser By Justin Minns

As a landscape photographer filters are an essential part of my kit. Neutral density (ND) filters allow me to control the shutterspeed for creative effects such as blurring water or clouds, while graduated ND filters are invaluable for balancing the light in unevenly lit scenes, when the dynamic range would otherwise exceed that of the camera. Top of the list though is the very useful but often underrated polariser which deserves a place in every landscape photographers bag.

Using a polariser

So what exactly does a polariser do? Without getting into the science too much, light becomes polarised when it bounces off a flat non-metallic surface, such as water or foliage as well as off moisture and pollution in the atmosphere. This polarised light is what causes reflected glare or haze which can reduce the intensity of colours in an image. A polariser simply filters out these unwanted reflections, the result is bluer skies, greener leaves, reduced or eliminated reflections, and greater clarity in the final image.

Polarising filters need to be rotated to change the angle of light that is filtered out, the effect can clearly be seen through the viewfinder so it’s just a matter of rotating the filter until the desired effect is achieved. The intensity of the effect can be controlled by changing the angle of the camera, the strongest effect coming with the camera at an angle of 90 degrees to the sun.

Linear v circular

There are actually two types of polarising filter: linear and circular. These terms refer to the way that the filter modifies the light waves that pass through it rather than the shape of the filter.

Linear Polarisers only allow light waves moving in one linear direction to pass through, something which can cause problems for modern camera’s metering and auto focus systems. With a circular polariser the light enters the lens in a circular patternand this is the one to use with digital cameras.

Add punch

Polarisers are best known for the effect they have on blue skies. On a clear sunny day, much of the light in the sky is polarised,and when used at 90 degrees from the sun the filter will deepen blues making white clouds will stand out dramatically. An effect that while working well in colour can add even more punch in black and white.

Big Suffolk skies.. Canon G1-X, 28mm, ISO 100, 1/400s at f/8. Hoya polariser.

Cut reflections

The other main use for polarisers is to cut or reduce reflections from water, revealing details such as rocks or sand patterns below the surface. A polariser is also invaluable for reducing reflections when shooting through glass. Of course there are times when you want the reflections but a polariser can still allow you to fine tune their intensity. Even glare is sometimes desirable, when low, golden hour light is reflecting from wet rocks, for example.

First light at Dovercourt, Essex. Canon 5D IV, 16- 35mm at 16mm, light ISO at 100, 0.3s at f/14.. Lee Canon polariser ND grad, tripod.

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Autumn colour at Felbrigg, Norfolk. Canon 5D II, 24-105mm at 45mm, ISO 100, 2.5s at f/8. Lee polariser, tripod.

Reduce glare

In the autumn months the attentions of many landscape photographers turn to woodlands to capture the autumn colours. Forests in autumn are invariably damp, so when photographing autumnal woodland scenes, the glare from light hitting the wet leaves can cause them to be too bright, reducing the colour or even blowing them out completely. In fact, even dry leaves will reflect some light but in either case circular polariser can be used to cut out this glare, producing richer more saturated colours

Brighten rainbows (below)

Changeable weather can be wonderful for landscape photography. Passing showers and sunny spells often provide dramatic light and rainbows. Rainbows are caused by light reflected in water droplets so a circular polariser can almost make them disappear but rotate the filter to just the right angle and it will enhance the colours and make them ‘pop’.

Changeable weather at Brightlingsea, Canon 5D MkIV, 24-105mm at 32mm, ISO 100, 65s at f/16. Lee 0.6 medium ND grad & Big Stopper with Tripod

Slow it down

Polarising filters reduce the amount of light reaching the camera’s sensor by 1-2 stops so can be used at a push as an ND filter to add a subtle blur to moving water or in combination with a stronger ND filter to increase the effect.

Increase contrast

Light reflecting off distant haze or, at the coast, sea spray can affect visibility. In the image below taken in the Tatra Mountains in Slovakia, a polariser was used to increase contrast by filtering out this reflective light.

The view from Lesnica, Slovakia. Canon 5D IV, 24-105mm at 45mm, ISO 100, 0.4s at f/16. Lee polariser & 0.9 soft ND grad, tripod.

A word of caution

Polarising filters aren’t without their problems, the most common is uneven polarisation. The effect of a polariser is at its strongest at a 90 degree angle to the sun and it’s weakest at 180 degree, so at certain angles the effect may be uneven across the frame most commonly appearing as a dark area in one part of of the sky. This effect is emphasized when using a wide angle lens as it can show a wider area of sky. It can be difficult to correct this problem in post-processing but it can be easily cured in camera, either by reducing the level of polarisation by turning the filter slightly, changing your shooting angle in relation to the sun or using a longer focal length.

Another occasion when a polariser can cause problems is stitched panoramas when the changing angle to the sun with each shot could cause a slight change across all the frames and make stitching difficult and the final result uneven, the best solution in this case is to avoid using a polariser altogether.

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