HTC stands for higher light transmission. All circular polarizing filters have to deal with loss of light, but at the HTC filters from B + W this loss of light is limited to the minimum. The filter factor of 2 to 3 is improved so that light loss in B + W filters HTC is only 1 to 1.5 stops, while there is often up to 3 stops of light loss in other circular polarizing filters. (Filter factor of 4 to 8). HTC filters ensure the highest image quality thanks to the use of the best polished glass. Also, the polarization film is selected to be of the highest quality. The XS-Pro Digital filter mounting is used in premium line B + W filters. The bezel is thinner than the standard F-Pro mount and therefore suitable for use on super wide angle lenses (wider than 24mm on full frame format). The XS-Pro Digital filter mount is equipped with threading on the both sides of the filter. This allows you to use the original lens cap of the lens, while the filter it is extremely thin. XS-Pro Digital filter mounts are made of brass material and therefore very rigid. Also, this type of mount has a matte black finishing, so that reflection is reduced to the minimum.