Canon EOS 5D Mark III Instruction Manual page 242

3 Setting the Time Code
Drop Frame
If the frame rate setting is 6(29.97fps) or 8(59.94fps), the time code's
frame count causes a discrepancy between the actual time and time
code. This discrepancy can be corrected automatically. This correction
function is called drop frame.
[Enable] : The discrepancy is corrected automatically by skipping
time code numbers (DF: Drop frame).
[Disable] : The discrepancy is not corrected (NDF: Non-drop frame).
When the frame rate is set to 4 (23.976fps), 5 (25.00fps), or 7
(50.00fps), the drop frame function does not take effect. (If 4 is set or [53:
Video system] is set to [PAL], [Drop frame] option will not be displayed.)
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