Download PolarView™ ND filter

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