Absorbs the ultraviolet rays which often makes outdoor photographs hazy and indistinct. A muliti-purpose fine-weather filter for color as well as black and white films. Also serves as a permanent lens protector. Hoya manufactures a full line of filters in both standard and Hoya multi-coated. The difference between Hoya's standard line and that of other manufacturers is that Hoya standard filters have one layer of anti-reflective coating applied to each surface of the glass. Many other manufacturers standard filters are bare glass, and bare glass can reflect as much as 9% of the light hitting it. This greatly increases the risks of flare and ghosting.