Polarising Filters stop reflections and glare from water, glass, foliage, blue skies and metallic surfaces. By rotating the front of there CPL filter, the area of reflection or glare can be targeted and removed allowing more colour and details in objects or surfaces that emit gale. Circular Polarising Filters act the same way your polarised sunglasses do, and just like your sunnies, these filters are most effective in bright day light.