About Field Separation And Pulldown - Adobe AFTER EFFECTS 7.0 Manual

ADOBE AFTER EFFECTS 7.0 99
User Guide
Each interlaced video frame consists of two fields. Each field contains half the number of horizontal lines in the
frame; the upper field (or Field 1) contains all of the odd-numbered lines, and the lower field (or Field 2) contains all
of the even-numbered lines. An interlaced video monitor displays each frame by first drawing all of the lines in one
field and then drawing all of the lines in the other field. Field order specifies which field is drawn first. In NTSC video,
new fields are drawn to the screen approximately 60 times per second, which corresponds to a frame rate of approx-
imately 30 frames per second.
A
B
C
Interlaced scanning of interlaced video fields compared with progressive scanning of a noninterlaced video frame.
A. For interlaced video, first, the entire upper field is drawn to the screen, from top to bottom, in one pass. B. Next, the entire lower field is
drawn to the screen, from top to bottom, in one pass. C. For noninterlaced video, the entire frame is drawn to the screen, from top to bottom,
in one pass.
Most broadcast video is interlaced, though emerging high-definition television standards have interlaced and nonin-
terlaced variants.
Noninterlaced video frames are not separated into fields. A progressive-scan monitor will display a noninterlaced
video frame by drawing all of the horizontal lines, from top to bottom, in one pass. Computer monitors are almost
all progressive-scan monitors, and most video displayed on computer monitors is noninterlaced.
The terms progressive and noninterlaced are thus closely related and are often used interchangeably, but progressive
refers to the recording or drawing of the scan lines by a camera or monitor, whereas noninterlaced refers to the fact
that the video data itself is not separated into fields. For example, it is possible with some modern cameras to use
progressive scanning to record two simultaneous fields per frame of interlaced video.

About field separation and pulldown

If you want to use interlaced or field-rendered footage (such as from NTSC video) in an After Effects project, you
will get the best results if you separate the video fields when you import the footage. After Effects separates video
fields by creating a full frame from each field, preserving all of the image data from the original footage.
When importing interlaced video that was originally transferred from film, you can remove the 3:2 pulldown that
was applied during the transfer from film to video as you separate fields so that effects you apply in After Effects don't
appear distorted.