The Tiffen Series 9 Self-Rotating Warm Linear Polarizer Filter is a mounted filter that includes rear and front threads that allow filter stacking when using third-party or custom filter holders. This filter's rear threads are intended to retain a Series 9 non-self rotating mounted filter that is already placed within a compatible filter holder. A supplemental effect is then provided in addition to that of the retained filter. The Tiffen Series 9 Self-Rotating Warm Linear Polarizer Filter's front threads can then accommodate an additional non-self rotating mounted filter, which can then be held in place with a Series 9 retaining ring. Alternatively, another Tiffen Series 9 self-rotating filter may be screwed on top of the Tiffen Series 9 Self-Rotating Warm Linear Polarizer Filter.
Once installed, this filter can create a warm cast over an entire image while helping to reduce reflections and glare by filtering out light that has become polarized due to reflection from a non-metallic surface. The light from the sun naturally becomes 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.
The warming effect of the Tiffen Series 9 Self-Rotating Warm Linear Polarizer Filter can be obtained under daylight when this filter is used on a film camera system with daylight film installed, or on a digital camera system with its daylight white balance setting selected. This filter's overall coloration reflects a mired shift value of +45.
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, is non-coated, and has approximately 40% average light transmission. It is constructed from optical glass for clarity as well as color fidelity and features an aluminum-alloy filter ring that can be rotated in order to adjust the intensity of the polarization effect.