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The Polarizer - the one stop image improver!

An article written for us by Roger Lee


One of the almost magical benefits of the digital age in photography is the fact that we can achieve all the effects of the filters used in film photography, plus a lot more, on our computers at home.

The big 'however' is the Polarizing Filter! These effects cannot be fully replicated even in Photoshop. If you are not using your filter on your camera the opportunity is gone...and that opportunity was the chance to improve your image,  sometimes dramatically...with no real effort!

Software developers have not yet managed to come up with a digital equivalent of this amazing aid to photography. Some have almost got it but not quite…which means that we actually have to do something as we take our photographs if we want the full benefit.

A couple of quick examples to whet your appetite before we go into any detail…




The top one is the normal picture – the bottom one  shows the effect of using a polarizing filter – no other adjustments were made!

One more example…





As with almost any photographic subject there is an amazing amount of information  on the internet about the polarizing filter. The object of this brief article is, as I said, to whet your appetite so that you actually go and buy a filter and start using it and have fun instead of wasting time reading in depth articles...  

All the images used in this article are taken straight off the camera with no post processing at all, so that you can see the full effect of the filter. Hence you may see sensor spots and other imperfections!

The filter consists of two specially ground glass filters mounted in one holder. The front filter can be rotated to vary the polarizing effect from zero to maximum. As a result of this construction the filters are both more expensive and thicker than other filters such a UV filters. Thinner versions are more expensive but have the big advantage of reducing vignetting or visible darkening of the corners of the image. This can happen when using wider angle lenses and is caused by the filter holder visibly obstructing the light around the edges.



       


The filter is mounted on the front of the camera lens and then rotated to achieve the required effect.



The Polarizing Filter does two important things – it increases colour saturation and reduces reflections. Polarizer's are placed in front of your camera lens and work by filtering out sunlight, which has been directly reflected towards the camera at specific angles. This can help significantly as the remaining light is often more diffuse and colourful.

Bear in mind that, as some light has been removed by the filter, the image will require a longer exposure. The angle of light that is filtered is controlled by rotating the polarizer itself, and, as you rotate the filter, you will see a range of effects on the scene in view.
A polarizing filter produces its maximum effect when one's line of sight is at right angles to the direction of the sun: A good way to visualize this is to aim your index finger at the sun while holding your thumb straight up. Everywhere your thumb points when you rotate your hand (while still pointing at the sun) is where the polarizer is capable of the strongest impact.
The effect of the filter on the image can vary significantly depending on the angle of the sun and the degree of rotation. The changes in colouring can be very subtle. The best way to get a feel for this is to rotate the filter while looking through the camera's viewfinder. The use of the filter does not automatically improve your image! You will gradually build up your experience in visualizing when best to make use of it.

It is easy to over darken the blue of the sky for example…











Subtle colour changes can be most effective…

Since a polarizer's effect varies with angle, results can appear uneven when using wide angle lenses. As the lens covers a wide angle of view, some parts of the image may, effectively, be at a different angle to the sun. This can give odd variations in the blue of the sky.

The polarizing filter is wonderful for photographing rainbows as, depending on the angle of the sun, it can have a really effective saturation effect on the colours…





Reflections

The ability of the polarizing filter to reduce reflections can have a marked
effect on your images. When direct reflections are reduced, a greater part of the subject's light is of the diffuse variety — resulting in a more colourful representation. Foliage will be rendered with a brighter green and flower
colours will appear more intense.



Without polarization



With polarization – reduced reflections off the foliage

Really dramatic results happen when one starts to deal with the effect on water reflections…


     

Before



After



Before



After

The effect on water reflections is not limited to just increasing the clarity…it can change the appearance of the whole image dramatically…



   
Before



After



The effect of the polarizing filter on scenic views alone is reason enough to invest…      
…in a polarizing filter!



All the other effects are bonus contributions!






They are primarily designed for DSLR cameras as they screw on in front of the lens…







                                                           … but improvisation is possible!     

This does work! I have tried it on a number of compact cameras - it requires a bit of dexterity but with practise if you are really keen…! As the filters are not inexpensive, I strongly recommend that you take your camera to the photo shop and try it out to make sure that the combination is technically feasible and that you are comfortable with all the fiddling.


So - The Polarizing Filter – a great addition to your photographic gear!






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