Photography Weblog

Photography through your eye..............

Sunday, January 7, 2007

Improve Your Photography With A Polarising Filter

A polarising filter is one of the handiest gadgets you can add to your kit bag, but before you rush out to grab one let's look at what they are and what they can do for us.

First of all, polarising filters come in two varieties, linear or circular. This refers to the way they are polarised, not their physical shape. If you are using an SLR camera the linear type can have detrimental effects on the metering and the auto-focus systems, so it's probably best to stick to the circular filters.

Assuming you are not using one of the filter systems such as the Cokin range, that have their own methods of attatching to the lens, you should bare the following in mind:

If you're using a compact camera that does not have through the lens viewing, look for a filter that has index marks on its rim. Without these it can be difficult to get accurate and consistent alignment.

With a wide angle lens a filter with a thick rim may cause vignetting by intruding into the edge of the field of view. Try to find one with a very narrow rim. Some are as thin as 3 - 4mm.

The rim will often be marked to confirm whether it is circular or linear polarised. Circulars are usually marked PL CIR whilst linear will only carry the PL mark.

You can check the quality of the filter before you buy. Look through it at a silver coin. A good filter will show the coin as black.

Check whether the rim is threaded on both sides. This will allow you to fit other filters on top of the polariser. If it is only threaded on one side, you will need to remove it to fit another filter directly to the lens, then mount the polariser on top of the other filter. As the polariser is likely to be on your lens a lot of the time, it's more convenient to be able to stack others onto it.

A wide range of filters are available from a number of manufacturers in sizes from around 25mm and upwards, so you should not have too much trouble finding one to fit your camera. However it is worth bearing in mind a point I have seen mentioned in some photography forums on the web. The general opinion seems to be that Japanese filters seem to suit Japanese lenses, whilst German filters work best on German lenses. The differences are unlikely to be critical, particularly as some Japanese cameras use German manufactured lenses, but it is something to bear in mind.

In the next article I will look at some of the ways a polarising filter can help improve your work.

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