Canon EOS-1D X Mark III DSLR Camera (Body Only) - Manual (Page 451)

Rotating Images
You can use this feature to rotate the displayed image to the desired orientation.
1.
Select [ : Rotate image].
2.
Select an image to rotate.
Turn the < > dial to select the image.
3.
Rotate the image.
Each time you press < >, the image will rotate clockwise as follows:
90°→270°→0°.
To rotate another image, repeat steps 2 and 3.
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