Clear Glass Ceramic is made with a special heat treatment that precipitates microcrystals of a mineral called spinel evenly throughout, giving the entire filter consistent strength.
Clear Glass Ceramic offers a Vickers hardness number of 700HV, helps to prevent scratches and chips, which can lead to breakage of the filter.
The new SIGMA filter made with Clear Glass Ceramic 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.
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.
All SIGMA filters are manufactured to meet same standard as Sigma lenses, and checked with SIGMA's proprietary Modulation Transfer Function (MTF) measuring system (A1)* using 46-megapixel Foveon direct image sensors.
The SIGMA WR CERAMIC PROTECTOR is a highly reliable filter with outstanding protective capability featuring advanced material.
Give your valued lenses the care they deserve with the true protector. Interchangeable lenses are the most important element of photographic expression, and to the photographer they are a valuable personal asset. To help photographers continue to use for many years the lens systems in which they have invested their time, knowledge, and budgets, SIGMA has developed original lens filters that meet the company's high standards of excellence. In developing its new protective lens filter, SIGMA has leveraged an unprecedented cooperative relationship with a glass manufacturer, resulting in a completely new type of glass called Clear Glass Ceramic.
With many applications in aerospace and other industries, glass ceramic is an extremely tough type of crystallized glass that serves as the foundation for Clear Glass Ceramic. While featuring the high transmittance required of optical devices, this advanced new material combines greater hardness than chemically strengthened glass and greater flexibility than sapphire crystal glass. These qualities make Clear Glass Ceramic the ideal material for protective lens filters.
*Among filters for interchangeable lenses as of December 2015 (SIGMA research)
In the chemically strengthened glass used in conventional high-strength protective filters, only the surface is strengthened through chemical processes. In contrast, Clear Glass Ceramic 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 Ceramic is the ideal material for protective filters. Clear Glass Ceramic 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 Ceramic 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).
Made with a special process that evenly precipitates microcrystalline spinel throughout the material, Clear Glass Ceramic offers a Vickers hardness number of 700HV. The new SIGMA filter made with Clear Glass Ceramic 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.
Since Clear Glass Ceramic 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 Ceramic offers very high transmittance, making it ideal for use as optical glass.
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.
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.
The SIGMA WR CERAMIC PROTECTOR features an advanced new material, the Clear Glass Ceramic, which is made using newly developed crystallized glass from glass manufacturer Ohara Inc.
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.
All SIGMA filters are made completely in Japan, including all individual processes applied in their manufacture.
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