The Rodenstock 67mm HR Digital Circular Polarizer Filter helps to reduce 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 polarizing filter 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.
A circular polarizer only differs from a linear polarizer in that it contains a quarter wave plane in addition to the linear polarizing filter. The addition of this quarter wave plane is to circularly polarize the linearly polarized light for the use of auto focus and exposure functions. Due to how the light is broken down and filtered with a linear polarizer, auto focus and exposure accuracy become skewed during use. When the light becomes circularly polarized, it permits the use of these functions.
To prevent internal ghosting and reflections, multiple layers of anti-reflection coating are included. These coatings also offer greater protection to the filter substrate and help it to stay clean for longer than with uncoated filters. The coatings associated with HR Digital filters results in an improved beading effect when in contact with water or oil for greater cleaning efficiency.
This filter is constructed from optical glass for increased optical clarity and color fidelity. Before being set within a thin brass filter ring that minimizes the potential for vignetting while enhancing durability and jamming prevention, the sides of its glass are blackened to help further eliminate internal ghosting and reflections from occurring along the filter's edge.