Multi-coated to minimize reflection at the filter surfaces which reduces flare and ghosting. MRC Coating (Multi-Resistant Coating) by B+W is not only an extraordinarily effective multiple layer coating, it is also harder than glass, so that it protects filters from scratches, and it is also water and dirt repellent.
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 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 2.3 and 2.8 (approx. +1.3 stops).
The F-Pro filter mount has a modified retaining ring, which is no longer threaded in from the front, but holds the filter glass in place from the back. This prevents the retaining ring from being accidentally loosened during the removal of an additional filter or a lens hood that has been screwed in too tightly.