Boxed. Like the B2 and B8, the B12 Dark-Blue Filter subtracts red and thus cools down colourations. B2 is a mild filter used with daylight film to remove the reddish tinge from sunrise and sunset shots. The medium-blue B8 corrects colour when clear flashbulbs are used with daylight film. B12 is a colour conversion filter which naturalises the red cast produced by photofloods when shooting indoors with daylight film.
Filter factor is 1.2 – 2.2.