My general purpose filter is an 81C, you lose 2/3 of a stop, it increases the temperature by 400 Kelvin.

Wouldn't be without it when doing outdoor portrait work with colour film, be it slide or negative.

The 81A and 81B do warm slightly and more slightly, but the really pleasing colour that the people whose pictures I have taken like, are ones with the 81C.

Mick.