B & W Filters: Worthy of the Finest Lenses B & W filters are manufactured in the style of the best optical lenses. Each filter is cut from raw cylinders of pure Schott/Mainz optical glass, the same glass used by the world s top lens manufacturers. The filter mounts are made of black anodized solid brass. These high-quality components, combined with B & W s modern production technology and rigorous quality control, produce the flattest possible filters. This precision flatness (plano-parallelism) and B & W s high-quality anti-reflection coating, which is applied to both sides of the filter, minimizes the possibility of image deterioration due to flare.