In the chemically strengthened glass used in conventional high-strength protective filters, only the surface is strengthened through chemical processes. In contrast, Clear Glass Ceramics is made with a special heat treatment that precipitates microcrystals of a mineral called spinel evenly throughout, giving the entire filter consistent strength. Combining much greater hardness than chemically strengthened glass and greater flexibility than sapphire crystal glass, Clear Glass Ceramics is the ideal material for protective filters. Clear Glass Ceramics is also resistant to cracking due to small scratches or chips. Since the risk of shattering and producing fragments is reduced, it also offers an enhanced level of safety.
Clear Glass Ceramics offers a Vickers hardness number of 700HV.* This is a level of hardness much higher than that of chemically strengthened glass, which is used in conventional high-strength protective filters. Moreover, this higher level of hardness helps prevent scratches and chips, which can lead to breakage of the filter.
*In the Vickers hardness test, a diamond instrument is pressed onto a material, and the indentation so produced is used to calculate the hardness of the material, which is expressed as a Vickers Pyramid Number (HV).
Conventional protective filter
10 times the strength of a conventional protective filter, 3 times the strength of a chemically hardened glass filter
Made with a special process that evenly precipitates microcrystalline spinel throughout the material, Clear Glass Ceramics offers a Vickers hardness number of 700HV. The new SIGMA filter made with Clear Glass Ceramics offers over 10 times the strength of a conventional protective filter and over 3 times the strength of a high-strength protective filter made with chemically hardened glass of the same thickness.
Conventional protective filter
Thinner and lighter overall, thanks to advanced new material
Since Clear Glass Ceramics is extremely strong, the SIGMA WR CERAMIC PROTECTOR is up to 50 percent thinner and weighs up to 30 percent less than previous SIGMA filters while offering a higher level of strength.
SIGMA’s Clear Glass Ceramics offers very high transmittance, making it ideal for use as optical glass.
Water-repellent (WR) coating
The WR coating reflects only 0.24 percent of visible light, thereby minimizing flare and ghosting. Its ability to repel both water and oil is also excellent: water drops bounce right off, and fingerprints are easily removed with a quick wipe. This coating also offers high lubricating ability, giving it more than ten times the scratch-preventing capability of SIGMA’s current Super Multi-Layer Coating. The coating’s antistatic function helps prevent static electricity from attracting dust and other particles, which can easily be blown off the filter when they do adhere.
High quality and compatibility with all SIGMA lenses
SIGMA has checked the compatibility of all SIGMA filters with all SIGMA lenses. In addition, SIGMA has confirmed that these filters allow light to pass through evenly throughout the image, from the center to the edges. All SIGMA lenses in its new lines are checked with SIGMA’s proprietary Modulation Transfer Function (MTF) measuring system (A1)* using 46-megapixel Foveon direct image sensors, and all SIGMA filters are also manufactured to meet this same exacting standard.
Use of newly developed advanced material from glass manufacturer Ohara Inc.
The SIGMA WR CERAMIC PROTECTOR features an advanced new material, the Clear Glass Ceramics, which is made using newly developed crystallized glass from glass manufacturer Ohara Inc.
Case ideal for filter storage
The storage case is made of a special acrylic that is both stronger and more flexible than conventional filter storage case materials. The outer acrylic case is molded so as to be integrated with the inner elastomer holder, creating a filter holder designed to last many years with minimal deterioration. The case is designed to be highly durable and not open or close accidentally during use. All of these individual benefits add up to a case that is ideal for filter storage.
MADE IN JAPAN
All SIGMA filters are made completely in Japan, including all individual processes applied in their manufacture.