skylight http://www.adorama.com/alc/taginfo/skylight Article: Protect your lens with Skylight or UV filters.Things to put in front of your lens <p><span style="font-size: small;">The advertised purpose of a Skylight or UV filter is to cut atmospheric haze by absorbing ultraviolet light. </span></p> http://www.adorama.com/alc/article/11566 Article: What's A UV Filter For?.Demystifying a common accessory <p><span style="font-size: small;">A UV filter is one of the most common accessories purchased by SLR lens owners. </span></p> http://www.adorama.com/alc/article/8401