Light rays which are reflected become polarized. Polarizing filters are used to select which light rays enter your camera lens. They can remove unwanted reflections from non-metallic surfaces such as water or glass and also saturate colors providing better contrast. The effect can be 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 2.3 and 2.8 (approx. +1.3 stops).
Linear polarizers are used with most manual focus cameras and are not recommended for auto-focus cameras.
This filter is 100mm x 100m (4x4") square and is 2mm thick. It is specifically intended for the Lee filter holder system and the entire filter holder must be rotated to vary the polarizing effect.