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 light amber / yellowish filter warms up the look by reducing the blue cast.

81ef has conversion 3800-3200k, exposure +2/3.