User Guide

Chapter 4 Working With 24p and Variable Frame Rate Video 63
Working With 24p NTSC Video
Techniques for transferring 24 fps video to 29.97 fps NTSC video have existed for many
years. Because NTSC video is interlaced (two fields comprise each frame), there are
actually 59.94 fields per second in NTSC video. To simplify matters, suppose the field
rate is 60 fields per second. In this case, it’s easy to see that 24 frames per second can
be mapped to 60 fields per second by using a 3 frame–2 frame pattern (referred to as
3:2 [or 2:3:2:3] pulldown). The first film frame is recorded on 2 video fields. The second
film frame is recorded to 3 video fields. Then the pattern repeats.
However, a transfer between 24 fps film and NTSC video must take into account the
fact that the field rate of NTSC video is actually 59.94 fields per second. To properly
transfer 24 fps film to 29.97 fps NTSC video, the film is slowed down slightly to
23.98 fps. This is how a traditional film-to-video telecine works.
Several camcorders have the ability to emulate this telecine process by exposing and
shuttering at 23.98 fps, and then adding a 2:3:2:3 pulldown when the signal is recorded
to tape at 29.97 fps. The result is NTSC-compatible video that looks similar to a
film-to-video transfer.
Note: Even though the 2:3:2:3 pulldown of a film-to-tape transfer is emulated by this
process, there are many other factors that to contribute to a “film look,” such as
exposure, resolution, color, depth of field and so on.
Most camcorders use a pulldown method referred to as advanced pulldown, which has
a 2:3:3:2 pattern instead of the traditional telecine 2:3:2:3 pulldown. The advantage of
this pattern is that it is more efficient for digital devices or applications (such as
Final Cut Pro) to remove and introduce this pulldown than the traditional 2:3:2:3
pulldown pattern.
In Final Cut Pro, you can remove the redundant fields during or after capture. Once
the redundant fields or frames are removed, you can edit at 23.98 fps. When you
have finished editing, you can output back to NTSC at 29.97 fps by reintroducing the
advanced pulldown (2:3:3:2) or the traditional 2:3:2:3 pulldown. If you are outputting
to film or progressive scan video, you don’t need to add a pulldown.