Polarizing Filters - a Second Look

Let's look a little closer at what we can expect to achieve from using a polarising filter. First of all, a quick reminder about what they do.

Functions of a Polarizing Filter

As mentioned in my first article on polarising filters, they come in two varieties, namely linear and circular. Using SLR cameras, whether digital or not, it's best to stick to the circular type as the linear ones can have detrimental effects on metering and auto-focus systems.

Now, what exactly do they do for us?

Polarising filters do for your camera just what polarizing sun glasses do for us. They remove a lot of the glare from bright sunlight and the reflections from glass or water. This will result in your photographs being much clearer with more saturated colours.

Holiday shots taken on the beach or by a lakeside will have far fewer distracting reflections from the surface of the water and much more colorfull skies. Any clouds in the sky will be better defined against a more saturated and colourfull sky. You will often even be able to see detail beneath the waters' surface due to the removal of reflected light from the surface.

To get the best results from your polarising filter, you will need to keep a couple of points in mind.

You can independently rotate the front element of a polarizing filter to change its effect on your image. This allows you to compensate for different angles of the relected light from the subject and vary the strength of the filters effect. Watch what's going on as you rotate the filter before taking your shot.

On some cameras and in some conditions it may not be too obvious what's going on in the viewfinder so remember to take a number of shots with the filter in different positions.

You will also need to take note of the position of the sun relative to yourself and the subject particularly on a bright day.

The polarizing filter will give best results when the light from the sun strikes the subject at an angle of around 30 degrees rather than shining directly on to it or from directly behind. Things will improve further if you and your camera also face the subject at a 30 degree angle such that the sun is not looking straight at you.

An illustration of this can be seen at the web site listed in the resource box at the end of this article.

As mentioned above, the sky can be much improved by using a polariser, which is usefull for landscapes but also for bringing a bit more life to the background of many types of image. Here is a usefull tip to help you get the most out of this type of shot.

Point your index finger at the sun and extend your thumb at 90 degrees to the left or right depending upon where your subject is. Pointing your camera in the direction of your thumb will result in the best results. You may have to compromise here as you may not be able to move your subject into the desired position!

One last thing to think about. Because the job of a polarising filter is to prevent unwanted reflected light affecting your image, it obviously reduces the amount of light getting into the lens. It will usually cost you between one and two stops-worth of light. You will need to compensate for this by opening up your lens aperture or reducing your shutter speed to compensate. You can also alter the ISO rating by changing from say, 100 that you may normally use, up to maybe 200 or 400.

Conclusion

I hope this has been usefull to you, as using a polarising filter will definately bring benefits, but as usual you need to understand a little about how it works its magic in order to get the best out of it.

Also remember that if you have spent good money on a quality lens it will all go to waste if you fit a poor quality filter. Spend wisely.