Six-Second Push, Twelve-Frame Morph
Dana is finishing a 30-second promo at 1920x1080, 23.976 fps. Assets: four 6000x4000 JPEG stills, two screen-recorded UI clips, and a 12-second interview soundbite. The client wants a 6-second slow push-in on each still, a fast whip-pan between the two UI clips, and a Morph Cut hiding a jump between two halves of the soundbite where the subject blinks. Dana keyframed Scale 100→115 with default linear keyframes on each still, stacked Lumetri and then Transform on every clip, and placed a 12-frame Morph Cut at the blink. The push-in looks mechanical, the Morph Cut reports insufficient frames, and the whip-pan flashes black at the edges.
1. Why does the six-second push-in look mechanical, and what would you change about keyframe interpolation and effect order?
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The mechanics come from the interpolation, not the 115% value. Default keyframes are Linear: the move starts at full velocity and stops at full velocity. Over six seconds the eye reads that as a snap at both ends.
- Select the first and last Scale keyframes, right-click > Temporal Interpolation > Ease In / Ease Out, or drag the Bezier handles into a shallow S-curve. Slow-in/slow-out over six seconds reads as a camera operator settling.
- A three-keyframe move (100 → 108 → 115) with the middle key biased early mimics an operator easing off, and hides any residual softness at the end of the move.
Effect order: the still is 6000px wide, over three times the raster, so resolution is not the issue. Putting Lumetri before Transform means the grade is evaluated on the full-size image and then resampled, which protects edge quality; reversing it grades an already-downsampled image. Either is defensible, but the hard rule is one scale stage only - a second scale from Scale to Frame Size double-resamples and is what actually softens the push.
2. Explain why the Morph Cut fails and what Dana should do instead.
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Morph Cut is not a dissolve - it synthesizes frames from the handles on both sides of the cut. It fails when:
- There is not enough clean material. Roughly one second is the practical floor and two seconds is safe. At 23.976, 12 frames is nowhere close.
- The framing or subject position shifts across the cut, so optical flow has no consistent field to interpolate.
- There is a trim, speed change or effect inside the handle region, which contaminates the source frames.
- The shot is not a locked-off talking head; background motion defeats it.
Options, in order: slip the cut a few frames to buy handles; if the take does not allow it, cut on the blink so the blink motivates the change and no morph is needed; otherwise use a 6–10 frame Cross Dissolve plus a subtle 2% scale offset, or make it an L-cut with the audio running under. Morph Cut is the wrong tool when the two halves differ in framing by more than a few frames.
3. How should the whip-pan be built so it never reveals black edges, and what would you do about playback?
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Black edges mean the transform is exposing raster that is not there. A whip pan built purely from Position keyframes slides a clip off its own edge.
Build order:
- Scale both UI clips to about 125–130% first, so there is overscan on every side.
- Keyframe Position, plus 2–3° of Rotation, across 6–8 frames with Linear interpolation - you want the abrupt velocity here, unlike the push-in.
- Use the Transform effect with Shutter Angle for real directional motion blur. Animating Motion > Position alone gives you a clean but unconvincing slide.
- Overlap the outgoing and incoming clips on V1/V2 by exactly the length of the move, so there is never a frame where the gap shows through. The whip is a transition between two live clips, not a move to nothing.
- Pre-render that section. Motion blur on 4K screen capture will not play real-time, and a single dropped frame inside an 8-frame move is extremely visible.