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.
For technical information, please see this
guide to exposure increases required for each density. For more information on CTC filters, please see this
CTC glass filters PDF.
Colour temperature conversion filters are also available in combination (as 1 filter) with
neutral density or
polariser filters: please see the
combination filters list for details.