The "high-end" polarizing foils of the Kaesemann-type filters are neutral in color, they have a higher efficiency than conventional polarizing foils and they are cemented between high-grade plano-parallel optical glass.  The resulting sandwich is then precision-polished again to achieve highly accurate plano-parallel surfaces.  Subsequently they are edge-sealed to protect the foil against humidity.  Brass mounts made on CNC-controlled machines ensure precise seating on the lens.  Discriminating photographers regards the B+W Kaesemann-Type Polarizing Filter to be the very best of all polarizing filters.  They are well suited for applications that require the highest possible imaging quality, especially with high-speed telephoto lenses and apochromatic lenses. 

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 (for instance when cleaning the filters), and it is also water and dirt repellent, thus facilitating filter maintenance.

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 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). Circular polarizers are specifically designed for use with auto-focus SLR cameras (They will also work on manual systems without problems) and video cameras. It does not influence the metering systems of these cameras.