Combine two of these filters together to create a variable polarising filter. Useful for increase contrast in some images, especially in daytime photography. You can also reduce the brightness of an object, usually the Moon or a planet in order to enhance the ability to see fine details. Also helpful for splitting binary stars by reducing glare and diffraction around the brighter star of the binary pair. Retains true color balance since all wavelengths are transmitted uniformly over the entire spectrum.