Hoya HRT 67mm Circular Polarizing + UV Filter: Hoya HRT 67mm Circular Polarizing filter is designed to block ultraviolet light and reduce the bluish cast of daylight while also helping to eliminate reflections and glare by filtering out light that has become polarized due to reflection from a non-metallic surface. The light from the sun naturally becomes partially polarized due to reflecting off electrons in air molecules, causing the light to scatter into what appears as haze. A filter with polarizing capability arranges, and filters, this directionally polarized light perpendicularly to the reflected light, allowing for the absorption of much of this light. This results in a noticeable reduction of glare and reflections from non-metallic surfaces and an increase in the saturation of skies and foliage. This circular polarize is ideal for use with digital cameras and auto-focus lenses where a linear polarize will often disrupt auto exposure and focus features.