sorry to sound dumb but what do these filters do? Any pictures taken by one Ian?
stolen from another site lol
Light moves through space, vibrating as waves in many different directions. Light which is polarized, however, only vibrates in one plane. A polarizing filter or “polarizer” is a lens filter which polarizes light along one plane. This can cut non-metallic reflections and enhance contrast under certain conditions.
Polarizing filters contain a layer of polarizing material which is laminated between two glass circles and mounted in a frame. You can then rotate this filter, which affects the amount of light passing through. Even at their “brightest” setting, however, polarizing filters reduce the amount of light entering the lens - they always cost a stop or so of light.
So what use are they? Well, polarizers are useful for cutting reflections from water and glass (ie: non-metallic) surfaces. They’re commonly used for cutting reflective glare off of windows, or for taking a photo of a lake without a reflection on the lake surface, for instance. They can also be used to darken blue sky (technically, increase the colour saturation of the sky since light scattered by Rayleigh scattering is polarized) and certain types of vegetation. The effect of a polarizer on the sky varies depending on the angle to the sun (known as Brewster’s angle). So a very wide-angle lens (wider than 24mm or so) with a polarizer will demonstrate differing amounts of polarizing across the frame, which may or may not be objectionable.
There are two basic kinds of polarizers - linear and circular. Linear polarizers work well with manual focus cameras, but they interfere with autofocus cameras. Circular polarizers contain another element - a “quarter wave” plate - which ensures compatibility of the filter with autofocus systems. So if you’ve got an autofocus camera - like any EOS model - be sure to use only circular polarizing filters. Note that polarization is one of the few visual effects provided by filters which strictly speaking can’t be simulated digitally in an image editing program