Lee Filters 4x4" Warming Polyester Filter Set (81, 81B, 81D, 85C) 81 - 81B - 81D - 85C Filters 81 converts 3300K to 3200K requiring +1/3 stop of exposure. 81B = 3500K to 3200K (1/3 stop). 81D = 3700Kto 3200K (+1/3 stop). 85C = 5500K to 3800K (+2/3 stop).