This high-quality Sigma UV Filter blocks the invisible UV component of light from the sky, which can cause blur and to which many color films react with a blue cast. UV Filters are ideal for photography in high altitudes (in the mountains), by the sea and in regions with very clean air. The pictures gain brilliance and disturbing blue casts are avoided. Because the glass is colorless, color rendition is not altered, aside from the elimination of the unwanted blue cast, and no increase in exposure is required. The colorless glass also makes a UV Filter very suitable as protection for the front element of your lens against dust, flying sand, sea water spray and the like, and it can be kept on the lens at all times. It is recommended for color and black & white film, as well as digital photography. Multi-Layer Coating for Superior Protection: Sigma has treated this filter with a multi-layer coating process, which, in addition to its UV-blocking qualities, makes these filters especially scratch-resistant. This coating does not affect the optic characteristics of the filter, but significantly optimizes the protective effects.