The Tiffen 3 x 4" Fog 1 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 1 density provides a greater amount of fog effect than the 1/2, but less than the 2, 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.