Nikon A2 filters are used for modest warming of photos taken on daylight film in shade, on overcast days, or by north window light. It is the equivalent of a Kodak 81A. The A12 filter is much stronger, for correcting tungston film for use outdoors. It is the equivalent of a Kodak 85.
Ive read that an 85B specifically is for correcting Tungsten film, not an 85?
Anyway i have a Hoya 85 for the same reason - warming up daylight colour film. Its fit for that purpose; the effect is strong, but not so much that I dont mind leaving it on all the time. I just like that look, and I couldn't get it with 81a/b.
However I also have an 85B for that I use for Tungsten film, and I probably would never use that with regular film.