Color Temperature Blue (CTB) correction gels are calibrated to raise color tempreature to 5500 Kelvin (Daylight).

• They are availble in several strengths and are primarily used to correct Tungsten (3200 Kelvin)to Daylight
• CTB (Full Blue) raises 3200 Kelvin to 5500 Kelvin
• 3/4 CTB (Three-Quarter Blue) raises 4700K to 5500K
• 1/2 CTB (Half Blue) raises 4100K to 5500K
• 1/4 CTB (Quarter Blue) raises 3500K to 5500K