The Tiffen 4 x 5" 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. There can also be a softening effect due to how the light interacts with the subject matter. The 3 density provides a greater amount of fog effect than 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 4 x 5" / 101.6 x 127mm.