In nature photography, filters are a must for some photographers and an absolute no-no for others. Some photographers insist that everything must be captured exactly as it was in nature, while others love the effects and improvements that they can get from a variety of filters.
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 sometimes 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 polarized sunglasses. It does not color the photo, but it reduces glare and reflection. As a result, natural colors 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 color of the sky, while the colored filter adds artificial color. A blue filter, for example would also turn white clouds a shade of blue, where the polariser leaves the clouds clear and white.
The polarising filter also increments 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 polarization. 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 polarization, 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 colors 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 color, 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 colorful skies. Eliminating glare and reflection can be an awful 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 streamlined green through your photo. Just like in the sky, the effect is not the same as simply using a colored filter; the polariser does not add artificial color, it enhances the clarity of the natural color.
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 effects of the filter also varies depending on 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 polarizing filter to your DSLR kit bag. You will not 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.