Conventions of Opening Sequences

There are a few conventions of opening sequences:

• The production company
  
• The distributor
  
• Credits - director/actors


• Establishes either the main characters/themes or


• Shows the disruption straight away (Todorov's theory)

I think that the opening sequence which establishes the main characters/themes is almost like an introduction to the film, during the credits it gives you an idea of what to expect - and going back to Field's theory it helps the audience decide if they are going to like it or not. Saying this, it doesn't mean that an introduction-style opening sequence is absolutely necessary, for example when the opening sequence shows the disruption to the equilibrium it doesn't give the audience an introduction it just goes straight into the action/storyline - and to me this indicates that the rest of the film will mimic this (very fast moving/exciting etc) and therefore won't take a very long time to get properly started - for example, unlike rear window.