Interchangeable lenses are crucial for photographic expression and serve as valuable equipment for photographers. Sigma has developed innovative filters for front lenses that meet high-quality standards and help photographers maximize their investments in time, experience, and money in their lenses. In developing the new protective filter for 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 with exceptional protective capabilities.

Glass-ceramic is a highly resistant, crystallized glass commonly used in aerospace and other industries. This advanced material offers higher hardness than chemically tempered glass and more flexibility than sapphire glass, as well as the high light transmittance required for optical devices. These properties make clear glass-ceramic ideal 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 the mineral spinel, giving the entire filter consistent hardness. The combination of higher hardness than chemically tempered glass and greater flexibility than sapphire glass makes clear glass-ceramic the perfect material for protective filters. Additionally, clear glass-ceramic is shatterproof, minimizing the risk of fragmentation into small pieces and providing increased safety.