Datasheet

22 chapter 1 ■ Setting Up a Composite
box to Upper Field First or Lower Field First (the field dominance should match the intended
output format). During the render, the program creates the appropriate interlacing. Note
that the interlacing will be successful only if QuickTime Movie, AVI (Video For Windows),
or Windows Media is selected as the output format; if you choose to render an image
sequence, the fields are combined without averaging or interpolation. On the other hand, if
a field-separated composition is not rendered with interlacing, half the information for each
frame is discarded and the final image quality may suffer (particularly if you’re using low
resolution footage for the project). You can mix and match field-separated and progressive-
frame footage in a composition with no penalty, although you should take care when you
set up a render through the Render Queue (the render will convert field-separated footage
into progressive frames or the render will convert progressive frames into interlaced fields).
Figure 1.20 (Left) Close-up of model lifting a water bottle. The dominant upper field, as seen in the viewer of the
Footage panel, is displayed. (Center) Lower field of same frame. Note the significantly higher position of the bottle and
index finger. (Right) Upper field of the same frame, as seen in the viewer of the Composition panel.
If you are working with D1 or DV footage, it’s generally best to leave the field domi-
nance interpretation to the program. However, you can choose a different field dominance
or select a field dominance for a different video format through the Interpret Footage dialog
box. To access this, select the footage name in the Project panel, RMB+click, and choose
Interpret
→ Main from the menu. You can set the Separate Fields menu to Off, Upper Field
First, or Lower Field First. If field dominance is chosen incorrectly for a piece of footage,
objects will appear to move erratically in the viewer of the Footage panel. If the footage pos-
sesses a field dominance but the Field Separation is set to Off, the fields are combined with-
out averaging and heavy artifacts appear around objects in motion.
Various interlacing/de-interlacing plug-ins, such as RE:Vision Effects Twixtor, are
available for After Effects and are generally superior to the program’s native tools when
handling interlacing tasks.
3:2 Pulldown in AE
As mentioned earlier in this chapter, a 3:2 pulldown is required when converting between
24 fps and 29.97 or 30 fps. If you drop 24 fps footage into a 29.97 fps composition, After
Effects automatically applies the pulldown by repeating frames of the 24 fps footage. To
remove the resulting hesitation in the movement, you can apply time warping and frame
blending (which is detailed in Chapter 12). If you drop 30 fps footage into a 24 fps composi-
tion, frames are removed from the 30 fps footage. To remove resulting skipping within the
movement, you can apply time warping and frame blending.
In addition, After Effects provides a means to remove a 3:2 pulldown that was previ-
ously applied to footage. For example, if motion picture footage was transferred to video
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