What Are Filters?
Filters are, in essence, bits of glass or Perspex that cover the end of your lens, creating different effects. The most common of these are UV filters, which people use to cut out UV haze and (primarily) to protect the lens from scratches. The second most common are Circular Polarizers, which is what we will be focusing on in this article.
Why should I use Circular Polarising Filters?
Circular Polarisers are used for darkening the sky, saturating colours, and removing reflections from shiny surfaces such as water. Ideally you want to take your pictures in such a way that leaves little post work (ie: Photoshopping) to be done, and a polariser is a good way to start. This picture on the right was taken on a very bright autumn day, and the polariser was most beneficial in bringing out the colours as well as allowing for a small f stop to be used to enhance depth of field (note the out-of-focus leaves in the foreground).
When Should I use a Circular Polariser?
Polarisers are best used out-doors in bright sunshine, or when you are trying to see through a reflective surface such as glass or water. You would use one when you are trying to get a photo of rock-pools, through a glass window, shooting a bright landscape, or any outdoor scenario with a lot of colour. Polarisers can be used indoors, but remember they are kind of like sunglasses for your camera, in that they darken your image, so make sure you have plenty of light to work with first.
Here is an example of a polariser being used to enhance foliage colour. As you can see, the leaves on the right look a lot lusher than on the left, which was taken without a filter. (Photograph courtesy of David J Laporte under a creative commons licence).
This photo is a prime example of a picture taken with a polarising lens; the sky is darker, you can see under the water, and the green moss on the rocks is far more vivid. (Photograph courtesy of Jiaren Lau under a creative commons licence).
How Do I Use a Circular Polarizer?
Circular Polarisers screw directly into your filter thread on the end of your lens. You will notice that the Circular Polarizer is made of two parts one piece that stays still attached to the lens, and a second that rotates on the outside. When you look through your viewfinder and rotate this part of your polariser you will notice the view change, with the shot getting darker or lighter depending on which way you turn the filter. You will also notice reflections diminish and colours enhance. From here it's a simple matter to select the stage you want and adjust your exposure.
Here you can see the reflection on the bowl of water without a filter, with the filter on low, and the filter on high. Bear in mind that the higher quality a Circular Polarizer is, the more it will be able to eliminate reflection and enhance your image. Remember, if you have a superior quality lens you don't want to put inferior glass on the end.
That's about it for now. We hope you have been inspired to experiment further with your photography.
Happy Shooting!
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