Kelvin
Also known as: K, colour temperature scale
The unit camera menus use to describe the colour of light, where lower numbers are warmer and higher numbers are cooler than most people expect.
Updated
What it means
Kelvin numbers describe the light rather than the correction. A value set in a camera says what colour the light is being assumed to be, and the camera then corrects for exactly that.
The scale runs backwards from intuition. Low numbers are warm orange light and high numbers are cool blue light, which is the reverse of how warm and cool are used about the numbers themselves.
It is the manual face of White balance. Choosing a figure rather than leaving it automatic is what stops colour drifting between clips, and the figure is the whole of that decision.
How it works in practice
Four values cover almost everything outdoors. Around fifty-five hundred for daylight, somewhat higher for shade and Blue hour overcast, lower for sunset, and considerably lower again for artificial light indoors.
Setting it slightly warm is a common choice. Skin and snow both read better a little warmer than neutral, and a deliberate bias is easier to keep consistent than chasing accuracy per clip.
Matching across cameras starts here. Two bodies set to the same figure produce clips that need far less work than two left to guess, which is where Color matching time is actually saved.
What to watch out for
Underwater the scale runs out. Depth removes red entirely, and no kelvin value recovers a colour the water absorbed, which is why a Red filter belongs on the housing rather than a setting in the menu.
Mixed light has no single answer. A rider in sunlight against a shaded wall produces two temperatures in one frame and a Color cast either way, and any value chosen is wrong for one half of the picture.
The tint control is a separate axis. Kelvin moves between warm and cool, and a green or magenta cast needs the other adjustment, which is why fluorescent light defeats a kelvin-only setting.
How RawClip handles it
Clips that disagree about colour temperature are brought into agreement while the sequence is assembled, which handles a card shot across changing light. Choosing a fixed figure at capture makes that step smaller and the result more consistent.