Interchangeable filters are essential elements of photographic expression and valuable components of a photographer's equipment. SIGMA has developed innovative filters for lens front elements that meet high quality standards and help photographers protect their investments in time, experience, and money. In developing the new protective filter, SIGMA collaborated with a glass manufacturer to produce a new type of clear glass-ceramic. The SIGMA WR Ceramic Protector, made from this advanced material, is an extremely reliable filter that offers excellent protection.

Glass-ceramic is a highly resistant, crystallized glass widely used in aerospace and other industries. This advanced material combines higher hardness than chemically tempered glass with greater flexibility than sapphire glass, while also providing the high light transmittance required for optical devices. These properties make clear glass-ceramic the ideal material for lens protection filters.

Conventional high-strength protective filters use chemically tempered glass, which is only hardened at the surface through chemical processes. In contrast, clear glass-ceramic undergoes a special heat treatment that ensures an even distribution of mineral spinel, giving the entire filter consistent hardness. Clear glass-ceramic is ideal for protective filters due to its superior hardness compared to chemically tempered glass and its greater flexibility compared to sapphire glass. Additionally, clear glass-ceramics are resistant to small scratches or chips, reducing the risk of fragmentation into small pieces and providing a higher degree of safety.