Appendix 1

Appendix 5
Understanding Time Code
Drop Frame Versus Nondrop Frame
There are several time code formats in use; however, they can be divided into two types: drop frame
and nondrop frame. The following is an example of nondrop frame (NDF) time code:
12:45:22:27
The fi rst set of numbers represents hours (12), the next are minutes (45), then seconds (22), and
fi nally frames (27). It can be identifi ed as NDF by the colon (:) in the last position. In this case, we
are looking at a frame of NTSC video. We know it’s not 24 FPS fi lm because the frame number is
27. There would never be a number higher than 23 in 24 FPS. In NDF, this is a simple counter; every
frame has a sequential number that identifi es it. It’s great for editing because you know exactly how
many frames you have in a shot. This number represents 1,377,687 frames.
But as this is a frame of NTSC video, the clock is not time accurate. Because the frame counter is
based on 30FPS and the real frame rate is 29.97 FPS, the clock is running .1 percent too slow. So if
we need to know exactly how long the video is, or if we need to record the time of day, NDF will
not work.
The following is an example of drop frame (DF) time code:
12:45:22:27
This can be identifi ed as DF by the semicolon before the frames number. In DF, a frame number is
skipped now and then to keep the clock time accurate. In nine out of every ten minutes, the 0 and 1
numbers are skipped. So, in this case, we know this video is exactly 12 hours, 45 minutes, 22 seconds,
and 27 frames long. Or it may have been recorded at 12:45 P.M. plus 22 seconds and 27 frames
(time code uses a twenty-four-hour clock). But we do not know the exact number of frames it
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