The Way the Film Is Shot Reflects How Each Character is Progressing
One interesting tidbit that comes from the featurette is how thoughtful Cooper was about filming each character. For instance, as Ally starts to become more famous, the camera becomes smoother and sharper. The colors go from Jackson's dull view to brighter and cleaner in a nod to the "bright light" of sobriety.
Jackson is already famous at the start of the film, so throughout the movie, Cooper made a conscious effort to shoot in a way that seems as if Jackson is avoiding the camera — you never see him full on until we reach the end of the movie, when he ultimately decides to take his own life, and he cannot hide from himself anymore.