Polarising Filters: Why You Should Have One (And Know How To Use It).

Nature photographers must all eventually make a decision about the use of filters. Some photographers swear by them, others want nothing to do with them.

For my own photography, I fall somewhere in between those two positions. I always try to capture my subject in natural light without artificial effects...but occasionally conditions require that to get the best results, I need a little help. That's why I have exactly one filter in my camera: a polarising filter.

A polariser is not much different to polarised sunglasses. It does not colour the photo, but it reduces glare and reflection. As a result, natural colours can appear stronger and more vibrant in your photos. The most obvious place this can be seen is in the sky, where a hazy sky can become a rich, saturated blue.

The difference between using the polariser and a blue filter, is that the polariser uses the natural colour of the sky, while the coloured filter adds artificial colour. A blue filter, for example would also turn white clouds a shade of blue, whereas the polariser leaves the clouds clear and white.

The polarising filter also increases the contrast between the sky and the clouds, making the cloud formation stand out more clearly against the background. An attractive cloud formation can be enriched to become a feature of real impact in your photo.

Polarising filters can be rotated on the lens to adjust the level of polarisation. It is important to practice with your polariser to get the most natural effects.

A polarising filter in the hands of an inexperienced photographer can be a frightening thing. You see, at maximum polarisation, the filter can produce some fairly extreme effects. The contrast in the sky can be so strong that some areas will become navy blue, even black. The saturation of other colours in the photo can also be exaggerated beyond recognition. These effects can certainly be eye-catching and impactful, but they go far beyond anything you could call natural.

The trick with a polarising filter is to find a level that reduces the glare and provides a nice saturation of colour, while maintaining a natural appearance. This is a simple matter of rotating the filter on the camera until you find the right level, and with experience you will get the hang of it.

There is a lot more to a polarising filter than just colourful skies. Eliminating glare and reflection can be an enormous benefit in all kinds of situations; even in the places you least expect.

One situation that might surprise you is in the rainforest. On a cloudy day under the canopy of the trees, you would not expect glare to be a problem. But there can be a lot of reflection off the glossy leaves of the rainforest vegetaion, and a polarising filter can reduce it significantly. The result will be a more saturated green throughout your photo. Just like in the sky, the effect is not the same as simply using a coloured filter; the polariser does not add artificial colour, it enhances the clarity of the natural colour.

Of course the elimination of reflections can also transform any photo of water, and shiny surfaces like the glass walls of a high-rise building. With practice, you will find all kinds of ways to employ your polarising filter.

There are some drawbacks. The filter will darken your exposures, so you will often have to use slower shutter speeds than you would otherwise (and keep your tripod handy). The usefulness of the filter also varies with the time of day, and your angle to the sun. Half the time you will simply be better off removing the polariser and taking your photo without it.

I recommend adding a polarising filter to your DSLR kit bag. You won't use it all the time. With expereince, you will learn to judge when to use it and when to leave it in the bag, but your photography will be richer for having a polarising filter handy when the situation calls for it.