Blue filter

Blue filters are used for colour conversion when exposing daylight-balanced film in artificial light (Hoya 80A, B and C), and to increase colour temperature when slightly cooler tones are required (Hoya 82A, B and C).

82-series filters should not be mixed with the 81-series warm-up filters as each cancels the effect of the other.

The filter factor for an 80A filter is generally 4 x. For an 80B filter it is generally 2.75 x, or 1.7 stops.