The 39mm PURE Harmonie Circular Polarizer Filter from Cokin 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.

When the 39mm PURE Harmonie Circular Polarizer Filter is applied, 77% of ultraviolet light waves are blocked at 400 nanometers, before which they are progressively eliminated, helping to limit the light that enters a camera to the visible spectrum. The appearance of blue casts that can occur while recording video or still photos under daylight that also features ultraviolet light is reduced, preserving color accuracy throughout the frame.

Cokin PURE Harmonie circular polarizer filters are constructed from Schott glass for increased optical clarity as well as color fidelity, and promote nearly flat attenuation of visible and UV light. This 39mm PURE Harmonie circular polarizer filter features a durable, lightweight, 4.75mm-thick aluminum-alloy filter ring assembly with a front ring that can be rotated to adjust the intensity of the polarization effect. These rings minimize the potential for vignetting, and the front ring also includes corresponding 39mm front filter threads for use with other screw-on filters.

To help eliminate internal ghosting and reflections, each glass surface of the 39mm PURE Harmonie Circular Polarizer Filter features 16 layers of Cokin's EVERCLEAR 5 anti-reflection coating. These coatings are resistant to oil, dust, dirt, and scratches, offering greater protection to the filter and help it to stay clean for longer than with uncoated filters. The coatings are also hydrophobic, resulting in an improved beading effect when in contact with water for greater cleaning efficiency.