The Tiffen 4 x 4" 85 Ultra Pol Circular Polarizer Filter combines both an 85 color conversion filter with a circular polarizing filter to blend the effects of both filter types into a single, convenient solution.
The 85 color conversion aspect of the filter provides a warming effect and decreases the color temperature from 5500K to 3400K, allowing the use of tungsten balanced film in daylight conditions.
The Ultra Pol circular polarizing aspect of the filter helps to greatly reduce reflections and glare by filtering out light that has become polarized due to reflection from a non-metallic surface. This results in a noticeable increase in the saturation of skies and foliage, as well as clearer imagery when photographing in hazy conditions. A circular polarizer differs from a linear polarizer in that it supports full use of a camera's autofocus and auto exposure functions.
There is a total filter factor of about 6x, requiring an adjustment of 2.6 stops for normal exposure. Tiffen filters are made using ColorCore technology, a process that involves laminating the filter substrate between 2 pieces of optical glass and grinding flat to a tolerance of 1/10,000th of an inch. This filter measures 4 x 4" / 101.6 x 101.6mm.