Circular polarizing filters are made for all cameras with beam splitters in
the light paths of their TTL exposure meter and with autofocus lenses. Circular
polarization has the same pictorial effect as linear polarization, but allows
for proper exposure metering and/or autofocus distance settings.
The “high-end” polarizing foils of the Käsemann-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 regard the B+W Käsemann-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.