The 67mm ND8 QuartzLine Solid Neutral Density 0.9 and Circular Polarizer Filter from PolarPro is a filter that combines a solid neutral density effect with a circular polarizer effect. When in use, this filter's 8x filter factor provides a 3-stop exposure reduction. Its 0.9 density creates a darkening of the entire image, allowing you to photograph with a wider aperture or slower shutter speed than normally required. By slowing your exposure time or increasing your aperture, you are able to control depth of field and convey movement more easily.
Simultaneously, this filter can help 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.
This filter is constructed from quartz glass for enhanced durability. To prevent internal ghosting and reflections, 16 layers of anti-reflection coatings offer scratch protection to the filter substrate while promoting clarity and color fidelity. The coatings associated with the PolarPro 67mm ND8 QuartzLine Solid Neutral Density 0.9 and Circular Polarizer Filter also result in an improved beading effect when in contact with water or oil, allowing for more efficient cleaning.
The quartz glass is set within a brass filter ring with side knurlings that can be rotated in order to adjust the intensity of the polarization effect. Together, the brass material and knurlings prevent jamming and provide additional strength, as well as a textured grip when mounting or removing this filter from a lens.