Tiffen Filters 4x4 80B Color Conversion Filter - 4480B
The Tiffen 4 x 4" 80B Color Conversion Filter helps to increase the color temperature from 3400 to 5500K, allowing the use of daylight-balanced film in tungsten-lit conditions. The cooling effect of this filter requires a 1.6-stop increase in exposure for normal results.
This filter is 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. It measures 4 x 4" / 101.6 x 101.6mm.