Custom White Balance
Setting white balance by photographing a known neutral target under the actual light and telling the camera to treat it as neutral.
Measured in
K and tint
In depth
This is the only method that is correct by measurement rather than by estimate, and it handles mixed and unusual sources that no preset covers. The target must be lit exactly as the subject is. Its weakness is that it must be redone whenever the light changes, which makes it a studio and copy-work technique rather than a reportage one.
Examples in practice
A grey card photographed on a museum's copy stand sets a custom balance that renders every painting's colours faithfully.