A bi-colour fixture provides adjustable white light over a specified correlated colour temperature range. It lets the crew move between warmer and cooler white settings without changing a physical correction gel for each adjustment.
What the label tells you
Traditional designs mix warm-white and cool-white emitters, but the label does not require every fixture to use the same LED architecture. Check the actual CCT range, tint controls and available modes. Tunable white is another common description.
Practical example
Use a warmer setting to work with tungsten practicals, then compare a daylight setting near a window. Meter the result at the chosen CCT: maximum output can vary across the range. Matching the Kelvin number is a starting point; tint, spectrum and camera response still affect the match.
Bi-colour versus full colour
A bi-colour control range does not automatically include saturated red, green or blue output. Likewise, green/magenta correction is a separate capability that must appear in the specification. Read the fixture’s colour modes and photometrics rather than inferring them from the product name.
Equipment examples
The Aputure LS 600x Pro and amaran 200x S are examples of adjustable-white COB fixtures. Compare their stated ranges and output data at the CCT required for the shot.
Related terms
CCT (Correlated Colour Temperature) · Duv · RGBWW · Photometrics