Radiant white clouds against a deep blue sky or the deep colors of fall foliage don't happen by chance. B+W polarizing filters (polarizers for short) augment the purity of the intrinsic colors and increase color saturation and are among the most important filters for analog and digital photography.
Because the filter mounts rotate, the polarization effect can be visibly controlled in the viewfinder or on the monitor display. Another effect of the B+W polarizer is to reduce reflections from non-metallic surfaces such as water, glass, and glossy paint. Objects and people behind surfaces such as shop windows and car windshields become visible again – a fascinating image enhancement without image processing!
B+W polarizing filters are circular polarizers which are compatible with nearly all modern cameras when beam splitters are used in the light path for TTL exposure metering or autofocus. Exposure errors are therefore avoided. The multiplying factor with HTC is 2 to 3, which is equivalent to 1 to 1.5 f-stops. Other polarizers up to approx. 3 stops. Often regarded as the most important filter for photography.