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. If you combine a Variocolor with a Neutral Polarizer, you can vary the intensity by rotating the Neutral Polarizer. For example, depending on the relative rotation of the VarioColor Red/Blue filter and the Neutral Polarizer, the reflections become either a red tint or a blue tint. The effect can be seen through the viewfinder and varies according to how the filter is rotated and its orientation to the sun.
This filter measures 130 x 170mm and only fits the Cokin X-PRO series holder.