The Clear-Night Filter for Sigma 14-24mm f/2.8 DG DN Art Lens for Sony E from Haida is designed to reduce the appearance of light pollution in images or video that include the night sky, and to minimize illumination from artificial light sources. This effect can be obtained when the filter is used on a digital camera system with the 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 sources can include streetlamps, exterior and interior lamps for commercial or residential buildings, sports and entertainment venue lighting, and brightly lit advertisements such as billboards. 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 discern individually. Light pollution from these "cluttered" sources can become a source of distraction within an image, and can resemble overexposed areas of glare.
The Haida Clear-Night Filter is a rear-mounted filter that can improve the results of nighttime images by absorbing the yellow light from sodium-vapor lamps, a common light source within urban areas. By preventing the dominant wavelengths of light associated with the color of those lamps from being recorded, the filter enhances visibility of astronomical objects. It ensures that, in the places where they do appear, artificial light sources are more clearly defined, with less glare and improved contrast.