Apple Shake 4 - Manual (Page 201)

Chapter 6 Importing Video and Anamorphic Film 201
With Inc set to 0.5, the playhead moves in half-frame increments as you scrub through
the Time Bar. When you use the arrow keys to move back and forth in the Time Bar,
you’ll actually be moving from field to field. The first field is displayed when the
playhead is on whole frames, and the second field is displayed at every frame and a half.
When Shake deinterlaces the media in your script, the even and odd fields displayed in
the Viewer are actually interpolated to fill in the gaps where the lines of the opposing
field were previously pulled out. This makes it easier for you to work with the individual
fields, and also improves Shake’s overall processing quality. For example, if you only
displayed the actual lines found in each video field, the images would look something
like this:
Field 1 appears in frame 1. Field 2 appears in frame 1.5.