Which brings us to the aforementioned “Mommy.” Considered a masterpiece, the film relies not only on the subject matter, but how it’s framed. To help the audience feel the claustrophobia and self containment of the main character, Dolan framed the majority of the film in a 1:1 square aspect ratio. When there are happy and emotional moments, or at the film climax, then he opens it up to the standard 1.85:1 ratio, making it wider and more natural.
These changes in the aspect ratio are essential to how Dolan tells the story, and invites the viewer into the experience, but when Netflix UK got their hands on the film, they did away with the aspect ratio changes, keeping the film at 1:1 throughout.
Naturally, Dolan was unimpressed the took to twitter with an open letter.