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When to use Field Dominance Override in Final Cut Pro

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Final Cut Pro can show combing, uneven motion, or the wrong field first even when the video itself is intact. Its Field Dominance Override offers four choices: Off, Progressive, Upper First, and Lower First.

That setting is useful, but it is easy to misunderstand. It does not deinterlace video. It does not change the frame rate. It does not perform inverse telecine. It tells Final Cut how to interpret the fields already in the clip.

What field dominance means

Interlaced video stores each picture as two fields. One contains one set of horizontal lines and the other contains the lines between them. The player needs to know which field comes first in time.

  • Upper First means the upper, or top, field is displayed first.
  • Lower First means the lower, or bottom, field is displayed first.
  • Progressive tells the player to treat the sample as one progressive picture rather than two interlaced fields.
  • Off means Final Cut follows the clip’s existing declaration.

If the order is wrong, movement can appear to jump backward and forward between fields. If truly interlaced footage is labeled Progressive, diagonal edges can comb because two different moments are being treated as one.

When an override is appropriate

Use an override only when the source is known to be field-based and its metadata does not describe it correctly.

Choose Upper First or Lower First when the footage is genuinely interlaced but motion shows the fields in the wrong temporal order. Most HD camera formats are Upper First, but the camera or capture format is better evidence than a rule of thumb.

Choose Progressive when progressive pictures were stored in an interlaced wrapper and you have verified that the two fields belong to the same moment. This is a metadata correction, not deinterlacing.

Leave progressive footage alone. A field override has nothing to fix on a source already declared progressive. Changing it introduces uncertainty where the file was unambiguous.

Field dominance is not reverse telecine

Soft telecine and hard telecine need different treatment.

With soft telecine, the file already contains the original progressive 23.976 film pictures. Repeat-field flags create the 29.97 presentation. ClipReady recognizes this only after progressive-frame and alternating repeat-field evidence agrees across several parts of the file. It can then place the same pictures on a uniform 23.976 timeline without re-encoding or dropping frames.

With hard telecine, fields from different film pictures are baked into the video. Changing Field Dominance cannot recover the original film frames. That requires real inverse telecine, which rebuilds the picture and falls outside ClipReady’s no-video-encoding path.

How ClipReady handles the setting

ClipReady calls Final Cut’s Off behavior As detected. It also offers Progressive, Upper First, and Lower First, but only after inspection positively identifies a uniformly interlaced source. For NTSC MPEG-2, several parts of the file must agree; mixed or inconclusive cadence shows no control because one field label cannot describe the whole clip.

The control is absent for progressive footage and for sources whose field structure is uncertain. The preparation engine repeats the same check, so a stale preference cannot silently relabel a progressive file. When a choice is accepted, ClipReady changes only the MOV or MP4 field declaration. Video samples and frame timing remain untouched.

Verified soft telecine is resolved first. When ClipReady restores its original 23.976 film cadence, the output is Progressive automatically and there is no separate field choice to make.

After preparation, ClipReady asks CoreMedia to read the field count and field order back from the finished file. A declaration that disagrees with the plan does not pass validation.

A safe rule of thumb

If you do not have evidence that the field declaration is wrong, use As detected in ClipReady or Off in Final Cut. The override exists to repair known metadata, not to experiment on a file that already plays correctly.