Canon EOS-1D X Mark III Advanced User's Manual page 661

3.
Edit and register information as needed.
Selecting [Add to camera] to applies the edited IPTC information to
the camera.
This also sets the camera's Custom Function [
information] option to [
Selecting [Clear camera info] deletes all IPTC information registered
on the camera.
This also sets the camera's Custom Function [
information] option to [
Selecting [Clear] clears all IPTC information.
].
].
661
8: Add IPTC
8: Add IPTC