Reflected light rays can become polarised, polarising filters are used to select which light rays enter your camera lens. These filters remove unwanted reflections from non-metallic surfaces such as water or glass and also saturate colours providing better contrast. The effect can be seen through the viewfinder and changed by rotating the filter. The filter factor varies according to how the filter is rotated and its orientation to the sun. Filter factor is between the 2.3 and 2.8, which is approximately +1.3 stops.
