Light rays reflected from surfaces can become polarised, so polarising filters are used to control which rays enter your camera lens. CIR-PL filters help reduce unwanted reflections from non-metallic surfaces such as water and glass, while also making colours appear richer, clearer and more contrasty. This effect is often used to boost the contrast and saturation of blue skies and white clouds. Hoya polarising filters do not alter the overall colour balance of your image.