The polarizing filter is still one of the most frequently used filters in photography. Polarizing filters only allow light of a certain oscillation plane to pass through. All other light rays are filtered out. This filtering results in a reduction of reflections on glass and water surfaces or paints. At the same time, the polarizing filters increase color saturation and enhance contrast. Objects located behind glass (shop windows, car windows) become visible again. In landscape photography, the polarizing filter develops its maximum effect at a shooting angle of 90 degrees to the sun. For an even effect in the picture, the focal length should not be less than 35 or 28 mm in 35 mm format due to the uneven polarization of the sky light. Circular and linear polarizing filters work on the same principle. Optical gratings on the filter foil ensure that only linear light waves whose orientation corresponds to that of the grating reach the lens. In contrast to a linear polarizing filter, the circular polarizing filter has an additional Lamda/4 plate. This platelet is responsible for the fact that the linear light rays previously produced in the polarizing filter are broken down again into all components and are at an angle of 90 degrees to each other. At the same time a component is delayed by a quarter wavelength. Thus, all polarization directions are again present behind the filter. This means that the autofocus problems often caused by polarizing filters do not occur with circular polarizing filters. The circular polarizing filter has excellent optical properties. The multi-coated, high-quality glass lens is embedded in a precisely manufactured metal frame. The rotating filter runs precisely and stops at the desired setting. It is transported in a protective cover that protects the filter from harmful UV radiation and thus significantly increases its service life.