Canon EOS-1D X Instruction Manual page 146

O Custom White Balance
Select image on card
First follow step 4 under "Record and register WB" (p.144) to take
a picture of a plain, white object. This image saved in the card can
then be registered for Custom WB. The procedure up to step 2 is the
same as in "Record and register WB."
In step 4, the following images cannot be selected: images captured while
the Picture Style was set to [Monochrome], multiple-exposure images, and
images taken with another camera.
To shoot with the registered Custom WB, first select the registered Custom
WB number, then shoot (p.147).
146
Select [Set Custom WB].
1
Select the Custom WB number to
2
be registered.
Select [Select image on card].
3
Turn the <5> dial to select [Select
image on card], then press <0>.
The images saved in the card will be
displayed.
Select the image to be used for
4
registering the Custom WB data.
Turn the <5> dial to select the
image to be registered for the Custom
WB data, then press <0>.
Select [OK].
5
Turn the <5> dial to select [OK],
then press <0>.
The Custom WB data will be registered.
When the message appears, press
<0> to return to step 3.