Colour temperature

Colour temperature describes the apparent warmth of a white source in kelvin. Lower numbers are warmer and more amber; higher numbers are cooler and bluer. Two reference points dominate production work: around 3200K, the colour of tungsten, and around 5600K, nominal daylight.

A camera is balanced to one value. Light a stage with fixtures of mixed colour temperature and the camera cannot be right for all of them, which is what produces the presenter with one green cheek and one amber one. This is why the fixtures in a shot are matched before anybody argues about levels, and why a window in a ballroom is a lighting problem rather than a view.

The quality number on the spec sheet is usually CRI, and it is a weaker promise than it looks. CRI averages eight desaturated test colours and leaves out saturated red entirely — which is the sample that most affects skin tone on camera. A fixture can carry a high CRI and still render faces poorly.

Better measures exist and are worth asking for by name. TM-30 reports fidelity and gamut across ninety-nine samples instead of eight. For anything being recorded or streamed, the camera-facing metric is the Spectral Similarity Index. CRI remains what most manufacturers print, so it is a floor to screen on rather than an answer.

Live streaming and broadcast — owned inventory, our own crew, and a site survey before anything is specified.

• Stage wash The even, flattering light a person stands in to be seen — the least glamorous part of a lighting plot and the first thing a camera exposes as missing.
• PAR fixture The simplest instrument in the rig — an oval pool of hard, bright light with its beam spread built into the lamp rather than adjusted at the fixture.
• Fresnel A soft-edged wash fixture with a stepped lens, adjustable from spot to flood by moving the lamp — and controlled at the edges with barn doors, because it has no shutters.