The artist himself decides the screen ratio.

“Dialectics of Cinema” by Eisenstein (1954, Kadokawa Shoten)

In this book, Eisenstein sometimes quotes Marx and Engels' dialectics.
In the second half of the book, he discusses and examines screen ratios.
When it comes to screen ratios, which are so important to filmmakers, is it enough to simply follow past customs or ratios determined by countries or companies?
Here, Eisenstein insists on the proportions of a gigantic square.
In Potemkin, he experiments with square proportions in one place (three places because it was edited) in the Odessa staircase scene. (However, unlike today, you can't change it freely on a computer, so it's just a mask placed in front of the camera, so it's blurry.)
Kiryukan also changes the screen ratio each time, albeit slightly.
Specifically, it is changed by covering the left and right or top and bottom with black masks. This is the same principle as the Vista size films.
This is a modest resistance and assertion that ''We, as experimental avant-garde artists, will not be at the mercy of the powerful or wealthy''.