Colour Temperature Conversion (CTC) glass filters are used to balance the colour temperature of a light source with the type of film used. Thus they will balance tungsten film to daylight or vice versa, providing significant changes in colour temperature of various light sources. These glass filters can also be used to create an intentional warm or cool effect.

This amber filter (orange tone) is used for exposing tungsten materials in daylight.

85b is used for exposing type B tungsten materials in daylight. Conversion 5500-5200, exposure +2/3.