Aspect Ratio Change (Xavier Dolan's Mommy)

Scene of the movie Mommy (2014) where the aspect ratio (1:1) change to 1.85:1.

[leona]

timothee chalamet mentioned this in an interview and i had to see it

[nicojarrin]

can someone share some light on how to do that actually ? i guess it most be something in after effects, but would be really nice a good tutorial

[gulamyazdani]

I downloaded the movie and waited for this particular moment but the aspect ratio didn't change. What's the matter?