Interchangeable lenses are essential elements of photographic expression and are part of a photographer's valuable personal equipment. Sigma has developed innovative filters for lens front lenses that meet the company's high-quality standards, helping photographers utilize their lenses for years, in which they have invested significant time, experience, and money. In creating the new protective filter for lens front lenses, Sigma collaborated with a glass manufacturer to produce a new type of material, clear glass ceramic. The Sigma WR Ceramic Protector, made from this advanced material, is an extremely reliable filter that offers outstanding protection.

Clear glass ceramic is a highly resistant, crystallized glass that serves as the basis for this new material and is widely used in aerospace and other industries. This advanced material combines greater hardness than chemically hardened glass with greater flexibility than sapphire crystal glass, while also providing the high light transmission required for optical devices. These properties make clear glass ceramic the ideal material for lens protection filters.

Conventional high-strength protective filters typically use chemically hardened glass, which is only hardened on the surface through chemical processes. In contrast, clear glass ceramic undergoes a special heat treatment that ensures an even distribution of the mineral spinel, giving the entire filter consistent hardness. The combination of greater hardness than chemically hardened glass and greater flexibility than sapphire crystal glass makes clear glass ceramic the perfect choice for protective filters. Additionally, clear glass ceramic is break-resistant, reducing the risk of splintering into small fragments and offering a higher degree of safety.