B+W polarizers have a foil, which consists of a grid construction, cemented between two pieces of glass. This grid construction is invisible to the eye, and it only allows light rays vibrating parallel to the foil grid to pass through. Light rays which are vibrating perpendicularly to the foil grid are totally blocked, while other directions are partially suppressed.
When light is reflected from a surface, a polarization of the reflected light develops. The degree of polarization depends on the angle of incidence of the light, which varies according to the characteristics of the material. Light reflecting off water surfaces has a maximum polarization of under 37 degrees, while reflection off glass is under 32 degrees. With the aid of a correctly positioned polarizer, reflections can be totally eliminated under ideal conditions. This occurs when the illumination angle and picture taking angle are almost equal and the angle of maximum polarization is in the range of 30 - 40 degrees. The effect of B+W polarizers can be observed through the viewfinder while rotating the front element of the polarizer.This filter uses our standard B+W rotating F-Pro filter mount, which has a front accessory thread and is made of brass. Compared to the earlier standard mount introduced in 2001, the F-Pro mount has become thinner. Now it can be used with wide angle lenses, including most 24mm focal lengths on a full frame body, without vignetting. Another advantage of the F-Pro mount is it's modified retaining ring, which is no longer threaded in from the front, but holds the filter glass in place from the back. When removing a filter or lens hood that has been screwed on too tight to the filter, the retaining ring is not at risk of loosening.