Drop Frame Time Code
Drop Frame time code was developed to
compensate for the error between 30
NDF time code and 29.97 NTSC signal
speed. In Drop Frame, the first two
frame numbers (:00 and :01) are dropped
at the start of each minute, except for
minutes ending in zero (0, 10, 20, 30, 40
and 50). In one “hour” of Drop Frame
time code, this amounts to 108 frames
(54 x 2 =108) skipped, or about 3.6 sec-
onds of real-time.
While Drop Frame time code is said
to be real-time accurate, it only synchro-
nizes to real-time at these 10-minute
marks (and even then it is not 100% ac-
curate), but it’s generally “close enough.”
Both types of NTSC time code may
be referenced to 60 Hz rather than 59.94
Hz; this is common in audio recording.
In this case, 30
NDF time code is “time-
accurate” and 30
DF time code runs 0.1%
faster than real time. Your calculator may
be set to run NTSC time code at either
59.94 Hz (the default) or 60 Hz.
For more information on video time
codes, refer to SMPTE Standard ANSI/-
SMPTE 12M-1995, available from the
Society of Motion Picture and Television
Engineers (SMPTE), White Plains, NY.
User’s Guide – 5