Canon EOS 5D Mark III Instruction Manual (en)

 Menu Function Settings
[52] Menu
HDMI frame rate
You can set the HDMI output frame rate to [Auto], [24p], or [60i/50i]. 
When you record movie from the HDMI output to a commercially-
available external recording device, set the frame rate to match the 
external recording device’s frame rate.
By pressing the <
B> button, you can change the information 
displayed on the screen.
You can append a time code to the HDMI output image (p.241).
If the frame rate set manually is not compatible with the external 
recording device, the frame rate will be set automatically.
If [Movie recording size] is set to frame rate 4 when [HDMI frame 
rate: 60i
] is set, “2-3 pulldown” will be performed.