Sigma Lens filter WR Ceramic Protect 67mm

• Made of clear glass ceramic
• 3 times harder than conventional, chemically tempered glass
• High translucency, minimized stray light and ghosting
• Water- and oil-repellent, scratch-resistant and antistatic WR coating

The Sigma WR ceramic protection filter is made of clear-glass ceramic, an extremely durable glass that is widely used in aerospace and other industries. This advanced material combines greater hardness than chemically tempered glass with greater flexibility than sapphire crystal glass. It also has the high light transmission required for optical devices. These properties make clear glass ceramics the ideal material for lens protection filters.

The chemically tempered glass used for conventional high-strength protective filters is hardened only on the surface by chemical processes. In contrast, clear glass ceramics are manufactured with a special heat treatment that ensures an even filling with the mineral spinel. As a result, clear glass ceramic has a Vickers hardness of 700 HV - which is 3 times as hard as chemically hardened glass filters.

The WR coating reflects only 0.24 percent of visible light, minimizing stray light and ghosting. The water and oil repellent properties are also excellent: water drops bounce off and fingerprints can simply be wiped off quickly. The antistatic properties of the coating also prevent the static adhesion of dust and other particles. These can easily be blown away by the filter.