“Aftersun” is intentionally ambiguous, which might frustrate viewers who prefer concrete answers. Sophie’s possession of Calum’s camera (and Turkish rug) proves that he is deceased, as does the film’s structure, in which she reassesses her memories and the videos of her journey. But, as the trope goes, if the audience never sees the body, the character isn’t dead for good. It’s possible (but highly unlikely) that Calum simply stopped being a part of Sophie’s life after her vacation.
The much more plausible explanation is that Calum continued to struggle with depression after Sophie boarded the plane home to her mother. From Calum’s perspective, she zigzags through the line and waves goodbye, which is the last thing he records. From the film’s perspective, Calum walks down an airport corridor and into the rave. This could mean he dies by suicide almost immediately after the events of the film, or it could be an abstract final note intended to convey Calum’s conflicting feelings rather than a definitive plot.
If he ended his life, “Aftersun” doesn’t seem interested in the details of how or when. It’s about Calum struggling between his role as a father and his reality as a person with severe mental health issues. He’s eager to share as much knowledge as possible with Sophie – like how to defend himself – as if he knows he’s on his way out. But he also makes promises like he’s there. Ultimately it is up to the viewer. However, with charged images like the Polaroid of Calum and Sophie, which we never see developed, Wells seems to provide a tragic if still ambiguous solution.