Canon EOS 1D MkII Instruction Manual page 50

Instead of a white object, an 18% gray card (commercially available) can
produce a more accurate white balance.
50
Import the white balance data.
4
¡Hold down the <
turn the <
let go of the <
The image's white balance data will be
s
imported.
Select <
5
O
¡Hold down the <
5
the < > dial to select <
go of the <
The custom white balance will be set.
s
X
> button and
5
> dial to select [OK]. Then
X
> button.
>.
B
> button and turn
O
B
> button.
>. Then let