Purpose ：The Clear-Night Filter 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. | Principle ：The filter 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, filter enhances visibility of astronomical objects. | Glass coating ：This filter is constructed from optical glass for clarity and color fidelity. each glass surface includes multi-coating of anti-reflection coatings, The Nano coating associated provides an additional layer that results in an improved beading effect when the surface comes in contact with water or oil, allowing for more efficient cleaning. | Frame：Ultra slim 3.07mm an aluminum alloy ring ensures durability while allowing the filter to remain lightweight. A plastic case is included for storage and transport. | Other：Please verify your camera's lens thread size before ordering. Your camera's lens thread size will be marked somewhere on the lens barrel or printed underneath your lens cap.If you have any questions about Haida products, you can contact us at any time .