Particularly designed for cameras with a polarizing half mirror (split beam metering) & Digital cameras. Increases the color saturation of blue skies, removes the unwanted reflections from non-metallic surfaces such as glass, water, etc... Use an angle of 45° from the subject & turn the filter into the holder to adjust the polarizing effect. Cokin A Series Filters are recommended for lenses between 36 & 62mm in diameter with a focal length over 35mm. Cokin square filters fit into a holder & are attached to a lens via an adapter ring. There is no need to duplicate filters to fit different size lenses. Up to three filters can be used at once to create unique effects. The photographer has control over the positioning of the effect on the photograph.