The B+W Circular Polarizer Slim MRC 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.

The Multi-Resistant Coating (MRC) is both an anti-reflection coating as well as a protective surface. It helps to increase light transmission by reducing reflections, scattered light, and ghosting. Additionally, it offers greater protection to the filter substrate and stays cleaner for longer than uncoated filters.

B+W filters are constructed from high quality Schott glass for increased optical clarity and color fidelity. The slim filters are specifically designed for use with wide angle lenses and are only 0.2" / 5mm thick. They do not have front threads for stacking additional filters.

Note: This filter ring's outside diameter is slightly larger than the actual thread size, and because of this you may be unable to attach the lens manufacturer's bayonet-mounted lens hood to the lens while using this filter. This is dependent on your specific lens and how thick the front rim of the lens is; with thinner, low-profile lenses usually being affected more.