The Tiffen 3 x 4" Combination 85B/ND 0.9 Filter blends both an amber color conversion 85B and a 0.9 neutral density filter. The ND filtration provides a 3-stop exposure reduction for darkening the entire image in order to photograph with a wider aperture or slower shutter speed than normally required. The 85B filtration covers the entire filter plane and converts the color temperature to 3200K for use with type B (tungsten) films.
This filter is made using ColorCore technology, a process that involves laminating the filter substrate between two 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.