converts tungsten light to daylight
Rosco CTB Blue overview. Roscoe Full Blue CTB Color Conversion Gel Filter - This filter is traditionally used to convert tungsten lighting to daylight. CTB (Color Temperature Blue) filters are available in a full spectrum of degrees (strengths) which, depending on your needs, can be used to either raise the temperature of your lighting or to create different lighting interpretations. CTB filters offer you complete control when shooting under tungsten lighting.