Ratio Switch

The shape of the frame changes during the film. Bars open outward or close inward, and the picture gets wider or narrower at a chosen moment.

It marks a change the audience feels before they name it. A frame that opens reads as release. A frame that closes reads as a world getting smaller.

The switch lands on a moment, usually a decision or a reveal, and it either cuts to the new shape or opens into it over a second or two. An animated open is more noticeable than a cut.

Composition has to work in both shapes, because the change is meant to be felt rather than studied. Shooting with the wider ratio in mind and protecting the narrower one is the usual discipline.

A video model will not switch shape mid run. Generate at the widest ratio and crop to the narrower one in the edit, then animate between the two crops.

Use it once, or twice, on a real structural break. A change of period, a change of point of view, a moment a character's world opens up.

Skip it as decoration. A ratio that keeps changing stops meaning anything, and the audience starts watching the bars instead of the film.

Masking blocks part of the frame with a shape and leaves black around an opening, and it is about what somebody is looking through. A ratio switch changes the shape of the picture itself, and it is about the film speaking to the audience.

The test is whether the change is motivated by a character. A keyhole or binoculars is masking. Bars moving with no in-world cause is a ratio switch.

Mommy (2014) runs in a square frame and then opens to widescreen at a moment of freedom, pushed open by the character on screen. The Grand Budapest Hotel (2014) gives each of its time periods a different ratio, so the shape of the frame tells the audience which decade they are in.

The model returns one fixed shape, because it cannot change ratio inside a run. Generate the widest ratio and do the change in the edit, as the note says.

The second failure is a composition that only works in one of the two shapes. Frame for the wider ratio and keep the important material inside the narrower one.