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LC-Tec Displays AB PolarView™ ND filter application notes March, 2014 PolarView™ ND filter APPLICATION NOTES Introduction Neutral density (ND) filters are used in photography for reducing the amount of light reaching the image sensor, enabling longer exposure times and larger aperture settings than otherwise possible. Their effect cannot be replicated digitally; hence they play an important role in many still and video camera applications. Picture from Wikipedia, courtesy: Robert Emperley, USA. Problem High performance digital cameras are normally designed to be sensitive in low light conditions, increasing the risk of over exposure in bright ambient light. To ensure optimal image exposure over a wide range of lighting conditions, the well-equipped photographer often carries a number of ND filters, each with a specific fixed optical density. Changing the filters can be cumbersome and there is a risk that other camera settings are changed unintentionally. This is especially problematic for videographers in situations where lighting conditions change rapidly. Recently, variable ND filters of rotating polarizer type have appeared on the market, but these also require manual handling. In addition, they provide only a limited dynamic range and a so-called “polarizer cross” artifact becomes visible at higher f-stop reductions. Some cameras are equipped with internal ND filters, but these too have fixed optical densities and must be mechanically activated. Solution The PolarView™ ND filter is an innovative electronic filter based on liquid crystal (LC) technology. Its optical density is simply controlled by adjusting the amplitude of an externally applied drive voltage. This fact offers several new user benefits: there is no longer any need for mechanical handling; a single PolarView™ filter offers an infinite number of well-defined optical densities within a wide range of f-stop reductions. The optical response is fully analog without any discrete steps. Fast, millisecond switching of the optical density allows the user to adjust the filter setting to rapidly changing lighting conditions. Furthermore, intelligent drive electronics enables automatic exposure control. A patent-pending configuration solves the problem of variation in angular transmittance properties present in existing variable ND filters and LC-based optical shutters. LC-Tec Displays AB │ Tunavägen 281, SE-781 73 Borlänge │ Sweden Tel: +46 243 79 40 70 │ Email: [email protected] │ Web: www.lc-tec.se Target applications High-end digital video cameras The PolarView™ ND filter, supplied with dedicated drive electronics, is designed to meet the highest industry requirements and fits into existing matte boxes mounted in front of the lens. It is optimized and commercialized for this application together with our partner Genus Limited (Hong Kong). Digital cameras with interchangeable lens Circular-shaped PolarView™ ND filters with compact drive electronics – compatible with available filter holders – makes it easy for the discerning photographer to benefit from the numerous advantages the filter possesses. Digital cameras with built-in lens Miniaturizing the PolarView™ ND filter enables integration inside smaller camera optics, directly substituting existing fixed optical density ND filters. PolarView™ advantages Analog f-stop reduction response Fast switching Manual or automatic adjustment Remote control compatible No “polarizer cross” No moving parts, ruggedized Low power consumption Main characteristics f-stop reduction range Angular transmittance characteristics Switching time Temperature range Size Transmittance (optical density) vs. applied drive voltage. Points correspond to integer f-stop reductions throughout the 2 to 12 range. PolarView™ 2 to 12 stops, analogue response No “polarizer cross” <50ms -30°C to +60°C Custom designing up to 14 x 16 inches Dynamic response when switching between f-stop reductions 2 and 12. For more information, please contact us at: [email protected]. © 2014 LC-Tec Displays AB PolarView™ ND filter application notes Page 2 of 2