The Tiffen 138mm WW IR Polarizer Filter is a combination linear polarizer and near-infrared to infrared control filter that is designed for digital cinematography. When this filter is used, it helps to reduce reflections and glare by filtering out light that has become polarized due to reflection from a non-metallic surface. Simultaneously, near-infrared light waves beginning at 680nm are blocked by approximately 80% and infrared light waves at higher frequencies are further impeded until nearly flat attenuation is achieved at 720nm.
This filter is useful as many digital motion-picture cameras are designed to maximize their ability to capture red hues, and in that process near-infrared or infrared contamination may occur. If the proportion of near-infrared or infrared light that reaches the sensor of a digital cinematography camera becomes too great, the results can show unwanted color shifts, particularly in dark areas of the frame such as shadows where the appearance of black is dominant.
While helping to preserve color accuracy when using a digital motion-picture camera, the Tiffen 138mm WW IR Polarizer Filter also addresses the effect of light from the sun becoming partially polarized due to reflecting off electrons in air molecules, causing the light to scatter into what appears as haze. A polarizing filter arranges, and filters, this directionally polarized light perpendicularly to the reflected light, allowing for the absorption of much of this light. This results in a noticeable reduction of glare and reflections from non-metallic surfaces and an increase in the saturation of skies and foliage.
A linear polarizer differs from a circular polarizer in that it does not contain an additional quarter wave plane. The addition of a quarter wave plane is to circularly polarize linearly polarized light for the use of auto focus and exposure functions. Due to how the light is broken down and filtered with a linear polarizer, in-camera auto focus and exposure accuracy become skewed during use. When the light becomes circularly polarized, it permits the use of these functions.
This filter is recommended when not using in-camera exposure metering or autofocus. It is non-coated with a 3x filter factor that results in a 1.6 stop exposure reduction. Constructed from Water White optical glass, the Tiffen 138mm WW IR Polarizer Filter is 138mm in diameter and mounted for use in third-party or custom filter holders. It is made using ColorCore technology, a process that involves laminating the filter substrate between 2 pieces of optical glass, grinding flat to a tolerance of 1/10,000th of an inch, and then mounting to precision metal rings. No front or rear threads are included on this filter's ring, or mount.