Eli5: How do you add CGI to an IMAX movie shot with real film?

Question

Eli5: How do you add CGI to an IMAX movie shot with real film?

In: Technology

Answer 1

Almost all movies are scanned in (if shot on film), edited digitally, then printed back onto film or simply distributed digitally. Since it’s edited digitally, adding CGI is trivial.

Unless Nolan’s directing it (and a few select other movies), then it’s all done on film. Options to get the CGI onto the film include printing it then splicing it in or compositing.

Or you can just not use CGI at all, then you don’t need to. (Nolan used no CGI shots on Oppenheimer). Either use practical effects, chemicals directly on the film, or a mix of both.

This question is really overly broad, and you might have better luck asking about specific techniques.