Aspect ratio still needs a stated conversion, not an assumption

The shot

Aspect ratio is the stated relationship between a frame's width and height, and matching it to a delivery format is a practical requirement documented on both the production and the vendor side. A filmmaking guide's overview of the subject defines aspect ratio as "the relationship between width and height of an image," usually written as two numbers separated by a colon, and states that "the most common film ratios used today in movie theaters are 1.85:1 and 2.39:1 as well as 16:9." A software vendor's own explainer on letterboxing adds that "most movies are filmed in a 2.35:1 or 21:9 ultrawide aspect ratio," and that footage shot in a narrower ratio needs black bars added, in Premiere Pro or otherwise, to read as that wider theatrical shape on a standard screen.

What the documents show

Both guides treat aspect ratio as a frame dimension that has to be set deliberately, either during capture or through a declared step afterward; neither describes a delivery ratio as something footage arrives in automatically. A generation vendor's own documentation shows the same principle applied to a generated clip: Runway's Edit Studio ratio-expansion feature states that its Expand Ratio tool fills in new frame area "without cropping your original footage or leaving empty space at the edges," using a named model to generate the added area, and lists explicit constraints on the source clip, including a required frame rate between 24 and 30 frames per second and a length between two and thirty seconds.

The workflow

Matching a generated insert to an existing edit's delivery format means treating the vendor's stated ratio-conversion step as a required stage rather than an assumption: generating or sourcing the clip within the vendor's documented input constraints, running the declared expansion or crop step, and previewing the result against the target ratio before it reaches the timeline, exactly as the guide's letterboxing method treats a mismatched capture ratio as a problem to solve in post rather than ignore.

What the tool does not change

No documentation reviewed here claims a generated clip's native output ratio will already match a specific delivery requirement; Runway's own feature exists because that gap is expected. Deciding whether an expanded or letterboxed frame still serves the shot's composition, rather than merely filling the target dimensions, remains an editorial judgment made by reviewing the result, not a property the conversion step guarantees on its own.

• Was the generated clip's frame rate and length checked against the conversion tool's stated input constraints first?
• Is the ratio conversion step documented as part of the brief, rather than assumed to happen automatically?
• Does the converted frame still serve the shot's original composition once previewed at the target ratio?

A delivery ratio has never been a property footage carries by default; it is a dimension a production states and then conforms to, and a generated insert is no exception to that stated step.