Cut on motion, and one frame before the failure

Why motion hides a cut

When the eye is tracking movement it is already processing change, and a discontinuity arrives as one more change among several. On a static frame, the cut is the only change and it is perceived as an event.

Editors have used this for a century: cut on the action, meaning cut during a movement rather than before or after it. A character begins to stand in shot A, and shot B picks them up mid-rise. The movement carries across the cut and the join becomes almost invisible.

The same rule protects you from mismatches. Two shots whose lighting differs slightly will cut together more happily on movement than on stillness, because the eye has something else to do.

Cutting on the action, practically

The technique: find the frame where the movement begins in shot A, then find the corresponding point in shot B, and overlap slightly. In practice, cut a few frames after the action starts in A, and pick up in B a few frames later than feels right. Movement reads as continuous even when the geometry does not quite match, and audiences forgive a great deal inside a moving cut.

In generative work you rarely have two shots of the same action, so the usable version is broader: cut while something in the frame is moving, whether or not the movement continues. A cut at the moment a car passes, a door swings, a figure turns, all of them absorb the join.

Cutting before the failure

The rule specific to this medium, and it is the reason the edit rescues so much.

You know where each take breaks, because you noted it in the selects pass. The shot ends one moment before that. If the hand goes wrong at six seconds, the shot is five seconds long, and nobody will ever know there was a sixth second.

This is not damage control. It is what editors have always done with real footage (end the shot before it stops working) and it is why the shot list should carry an intended length that you are willing to shorten.

Two consequences worth planning around: generate longer than you need, and never plan a sequence where one shot has to carry an exact duration. Music-video work is the exception and it is harder for exactly this reason.

J-cuts and L-cuts

The two most useful tools for making a sequence feel connected rather than assembled.

• J-cut: the audio of shot B starts before its picture. You hear the next scene before you see it.
• L-cut: the audio of shot A continues over the picture of shot B. You see the next scene while still hearing the last.

Both work because the audio and picture cuts no longer land in the same frame, so there is no single moment where everything changes. They are the difference between a sequence that feels edited and one that feels stapled.

In generative video they do an extra job: because each generated clip has its own audio situation and its own ambience, overlapping audio across the cut disguises the fact that the shots were never in the same place.

Cuts that read as mistakes

Three to avoid:

• The jump cut. Two shots of the same subject at nearly the same size and angle. Unless it is a deliberate style, it reads as a fault. Change size by at least two steps or change the angle substantially.
• Crossing the line. Covered in the directing module. Enforce screen direction in the stills.
• The cut on a static held frame with no motivation. If nothing is moving and nothing has prompted a change, the cut arrives as arbitrary. Give the audience a reason: a look, a sound, a movement.

The transition question

Use cuts. A dissolve means a passage of time or a change of place; a fade means an ending. Everything else in the transitions menu is a 1998 wedding video.

There is one generative-specific exception worth knowing. If two shots will not cut together (mismatched light, a colour you could not fix) a very short dissolve of four to eight frames can blur the join enough to pass. It is a patch, it is visible if you look, and it is better than the cut it replaces. Use it sparingly and never as a default.

Today: take two shots that refused to cut together and move the cut point to a frame where something in the outgoing shot is moving. Compare.