When you want to transfer film to a DVD video, you need
to use special techniques. Movies made on film are shot
using a frame rate of 24 frames per second. While PAL/SECAM
video has a frame rate of 25 frames per second, and NTSC
video 29.97 frames per second.
These frame rates are too low for viewing on a television
screen without getting flicker. Each frame on film is
projected twice, giving a display frame rate of 48 frames
per second. Unlike film, video frames each comprise two
interlaced fields, so that the field rate is 50 and 60 per
second for PAL/SECAM and NTSC. These are then high enough
for a flicker free moving image. The use of interlaced
fields reduces flicker without reducing resolution.
When converting film to video it is necessary to convert
the frame rate. Film to PAL conversion usually involves
speeding up the film from 24 fps to 25 fps and using a pitch
correction for the audio.
(See this
guide)
Converting film to NTSC video uses a 3/2 pulldown (ie
alternately converting frames to 2 and 3 fields) where a
group of 4 frames are converted to 5 frames or, actually, 10
fields as shown below:
3/2 Pulldown for film to
video transfer

The two extra fields are B1 (the first field of frame B) and
D2 (the second field of frame D).