Canon EOS-1D X Mark III DSLR Camera (Body Only) - Manual (Page 756)

Auto Rotation
You can change the auto rotation setting that straightens images shot in vertical orientation
when they are displayed.
1.
Select [ : Auto rotate].
2.
Select an item.
On
Automatically rotates images for display on both the camera and
computers.
On
Automatically rotates images only for display on computers.
Off
Images are not automatically rotated.
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