The 0.3 Filter Wheel #3 81A Light Balancing Filter from Tiffen helps control the bluish coloration that affects daylight film, it can also help reduce excessive blue from electronic flash. This filter is inserted ibnto your Filter Wheel #3, which allows you to rapidly cange filters within your lens, avoiding ned need to mount a filter on the front of your lens, and the filter wheel itself is sealed, keeping your filters clean and dust free.
81A
It's Autumn. The clouds are low hanging and the sky is "patchy blue." You've gone for a ride upstate to the mountains and the light in open shade is bluish. A photo taken of your girlfriend with daylight balanced film leaning against the side of a barn will yield bluish tones that she might not find particularly flattering. An 81A filter will replace some of the yellow missing from the image and bring her skin tones back to a more appealing level.