About Field Dominance
Field dominance is an issue when recording and playing back interlaced video material.
With progressive video, there is only one way to play back a video frame: start at line 1
and scan until the end of the last line. With interlaced video, the video player must
know whether to scan the odd lines first, or the even lines. In other words, each time a
frame is displayed, which field should be displayed first, field 1 or 2? The field displayed
first is totally dependent on which field was captured by the camera and recorded first.
Each field is a snapshot in time, so if field 1 is recorded earlier in time than field 2, field 1
must be played back before field 2. If the wrong field order is chosen, each frame’s fields
play backward in time, even though each frame as a whole still moves forward. The effect
is a very noticeable stutter happening 60 (NTSC) or 50 (PAL) times a second.
Each piece of video equipment and each video format has a preferred field dominance.
This prevents you from, say, editing two field 2s back to back, and makes sure that each
field is played back in the right order.