Canon EOS-1D X Mark II DSLR Camera (Body Only) - Manual (Page 178)

B : Setting the White Balance
178
To the human eye, a white object looks white regardless of the type of
lighting. With a digital camera, the white for color correction basis is
decided depending on the color temperature of the illumination, and
then the color is adjusted with software to make the white areas look
white. With this function, pictures with natural color tones can be taken.
White Balance
You can also set this with the [ z 1: White balance ] screen.
To switch between Auto [ Q ] (Ambience priority) and [ Q w ] (White
priority), use the [ z 1: White balance ] screen (p.179).
To set Personal white balance, select [ P : PC-* ] in step 2 on the
preceding page. To register a Personal white balance to the camera,
refer to the EOS Utility Instruction Manual (p.554).