In theatre, actors have to perform live, so they need to be loud and clear to reach everyone in the audience. In films, actors can do many takes and use close-ups to show small facial expressions.

In theatre, actors can hear and see the audience's reactions, which might change how they act during the performance. In films, actors don’t have an audience and just focus on the camera and what the director tells them.

In theatre, actors need to use big gestures and speak loudly because they are far from the audience. In films, actors can be more subtle because the camera shows everything up close.

In theatre, what you perform is what the audience gets; there’s no changing it afterwards. In films, there’s a lot of editing and adding effects after filming, which can change how the performance looks in the end.