Our blue cooling filters are used to balance out any reddish orange hues. These filters raise the overall color temperature value and are generally used to adjust the white balance when shooting in tungsten or fluorescent lighting. The -120 mired value raises in color temperature is now referred to as the C12 filter. There are 4 incremental variations in cooling filters offered: -20, -40, -80 and -120 mired values. Mired: Contracted from the term micro reciprocal degree, the mired is a unit of measurement used to express colour temperature. It is given by the formula: M (Mired) = 1000000/T (kelvin: Colour Temperature) The increase and decrease by colour temperature and the mired value become the opposite direction since the formula is a reciprocal. Filter type: filter factor: 3.0 f-stops: 1 2/3 mired shift: -120