Film set in time before an existing work—reveals backstory or character origins. Only works when audiences already know the original.
A prequel only works if the audience is familiar with the film to which the backstory relates. That is the crucial point — without this emotional anchor for the viewer, the story becomes arbitrary. You sit in the editing room and immediately realize: the tension doesn't arise from the plot itself, but from the knowledge of where it leads. This is a completely different dramaturgical mechanism than with the original.
On set, this means specifically: you need to know which visual or narrative threads from the original you want to pick up. Continuity is not optional — it is the foundation. If the characterization of an antagonist in the original is based on a specific trauma, this must be consistently prepared in the prequel. This sounds simple, but it is brutally difficult. You cannot invent character traits arbitrarily; everything must logically lead to what the audience has already seen. At the same time, you cannot simply copy the beats of the original — then it appears repetitive and manipulative.
In practice, you see this in the scenery and set dressing: what does the world look like before the catastrophic events of the original changed it? Is it brighter, more chaotic, more primitive? These details are not decoration — they are narrative information. The same applies to camera style and color grading. A good prequel manages to create a different mood visually while still fitting visually with the original.
The biggest risk: you tell something nobody wanted to know. A backstory can weaken the original in retrospect if it resolves the mysteries or the emotional power instead of deepening them. Some things are stronger when they remain secret. The best prequels — and I'm speaking from experience here from working through various cuts — expand the world instead of explaining it. They show why the world is the way it is, not just how it became that way.