Ordinarily, interlaced fields aren’t apparent to a viewer. Because each field captures the subject at a slightly different moment in time, playing a clip in slow‑motion, creating a freeze frame, or exporting a frame as a still image makes the two fields discernible. In these circumstances, it’s usually preferable to deinterlace the image—that is, eliminate one field and create the missing field either by duplicating or interpolating the lines of the remaining field.

Another unwanted effect can arise from inadvertently reversing the field dominance, determining the field on which edits are registered. When the field dominance is reversed, motion appears jerky. Fields can become reversed in the following situations:

• The field dominance of the original videotape was the opposite of the field dominance of the video‑capture card used to capture the clip.

• The field dominance of the original videotape was the opposite of the field dominance of the video‑editing or animation software that last rendered the clip.

• You have set an interlaced clip to play backward.

  You can process fields for an interlaced clip in the sequence so that the clip’s picture and motion quality are preserved in situations such as changing the clip speed, playing a clip backward, or freezing a video frame.