Canon EOS-1D C - Manual (Page 50)

50
3 Setting the Time Code
If the frame rate setting is 6(29.97 fps) or 8(59.94 fps), 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).
The time code will be displayed as follows:
[Enable] (DF) : 00:00:00. (During playback: 00:00:00.00)
[Disable] (NDF) : 00:00:00: (During playback: 00:00:00:00)
Drop Frame
When the frame rate is 4 (23.98 fps), 5 (25.00 fps), or 7 (50.00 fps),
there will be no dropped frames. (If 4 is set or [53: Video system] is set to
[PAL], [Drop frame] option will not be displayed.)