The Tiffen 4 x 5.65" 81B Light Balancing Filter helps to decrease the colour temperature by 300K to slightly warm the image to match the colour quality of the lighting. By using an 81B filter, you will be able to achieve a 3200K balance when the dominant light source is 3500K. The warming effect of this filter requires a 0.3 stop exposure increase for normal results. This filter is manufactured using ColorCore technology, a process that involves laminating the filter substrate between 2 pieces of optical glass and grinding it flat to a tolerance of 1/10,000th of an inch. It measures 4 x 5.65" / 101.6 x 143.5mm. - Light balancing filter decreasing colour temperature and providing a warming effect. - Subtracts 300K to achieve 3200K colour balance from 3500K lighting. - Filter factor of 1.3 requires a 0.3 stop exposure increase. Specifications