The Tiffen 3 x 4" Double Fog 3 Filter simulates the effects of natural fog or mist by creating a soft glow around highlights and lowering the overall contrast of the scene. When compared to the standard Fog filter, this filter places greater emphasis on lowering the contrast while maintaining sharpness and minimizing the effects of flare. The 3 density provides more fog effect that the 2, but less than the 4, and requires no exposure compensation.
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 3 x 4" / 76.2 x 101.6mm.