The 77mm HD MCR PureNight Filter from H&Y Filters is designed to reduce the appearance of light pollution in images or video that include the night sky and illumination from artificial light sources. This effect can be obtained when this filter is used on a film camera system with daylight film installed or on a digital camera system with its daylight white balance setting selected.

Light pollution occurs in areas of the night sky that are above or near concentrated and intense sources of artificial light such as cities. These light sources can include exterior and interior lamps for commercial or residential buildings, brightly lit advertisements such as billboards, streetlamps, as well as sports and entertainment venues. Together, they can result in a type of light pollution known as skyglow, where individual stars, the Milky Way, and other astronomical features in the night sky are obscured. Additionally, artificial lights clustered together can become difficult to individually discern. Light pollution from these "cluttered" sources can become a source of distraction within an image and can resemble overexposed areas of glare.

When used, the 77mm K-Series Night Filter can improve the results of nighttime images by absorbing the yellow light from sodium-vapor lamps, mercury-vapor lamps, or low Colour Rendering Index LEDs, common light sources within urban areas. By preventing the dominant wavelengths of light associated with the color of those lamps from being recorded, the visibility of astronomical objects is enhanced, and artificial light sources are more clearly defined with less glare and improved contrast.

This 77mm K-Series Night Filter is constructed from optical glass for clarity as well as colour fidelity and features an aluminum alloy filter ring for durability while remaining lightweight. Each side of this filter includes eight layers of anti-reflection coating to prevent internal ghosting and reflections as well as an anti-smear nano coating for an improved beading effect when in contact with water or oil for greater cleaning efficiency.