Polarisation filters influence which lightbeams reach the lens. For example, you can set them to remove undesired reflections in water or glass from your image. Or you could use a polarisation filter to influence the saturation or contrast of your image. 

These filters are often used to make the sky more blue. The effect of a polarisation filter is optical, so you can immediately see the results through your finder, LCD screen or monitor. You can vary the effect by turning the filter. The filter size is 67 mm.