When light from the sun bounces off a flat non metallic surface, such as glass or water, it becomes polarised with all of the reflected light waves vibrating in the same plane. This reflected glare can be removed by the polarising filter.
There are two types of Polariser, circular and linear. These names bear no relation to the physical shape of the filter itself but refer instead to the way the light waves are transmitted through the filter to achieve the polarising effect.
The Seven5 System features its own circular polarising filter.
Seven5 Circular Polariser
A unique clip-on design means this can be snapped onto the front of the Seven5 Holder and rotated independently of any graduated filters also in use. Reduces exposure 1⅔ stops when fully polarised.