SIGMA WR Ceramic Protector filters use unique Clear Glass Ceramics providing excellent scratch and shatter-resistance when compared to conventional high-strength protective filters. Clear Glass Ceramics are made using a special heat treatment that evenly distributes microcrystals of a mineral called spinel throughout the glass, producing a tough filters with a Vickers hardness rating of 700HV*.
*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).
SIGMA filters made with Clear Glass Ceramics offer over ten times the strength of a conventional protective filter and over three times the strength of a high-strength protective filter made with chemically hardened glass of the same thickness. WR Ceramic Protector filters are also 50 percent thinner and weigh up to 30 percent less than previous SIGMA filters. The WR Ceramic Protector is recommended when shooting in challenging environments as they can withstand heavy impacts which would otherwise shatter a conventional filter.
The weather-repellent (WR) coating effectively minimises flare and ghosting and has the ability to repel water and oil that can accumulate on its surface when shooting in challenging environments. When compared to conventional protection filters, the WR coating provides ten times more resistance to scratches. Its antistatic capabilities help prevent the build up of static electricity that can attract dust and other particles.
SIGMA has checked the compatibility of all SIGMA filters with all SIGMA lenses and has confirmed that Protector Filters allow light to pass through evenly throughout the image, from the centre to the edges. All SIGMA lenses 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 manufactured to meet this same high standards.
The included 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 specially moulded to make it durable to impacts, while the elastomer holder keeps the filter securely in place. It has also been designed to not open and close unintentionally when being transported.
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