Identifying Conventions of Posters - Introduction

As I am going to be making a poster, I want to look at some existing film posters to identify the general conventions of posters.

I have chosen to look at five posters from films of different genres to see if the conventions are consistent, regardless of genre.

The posters I am going to analyse are from the following films:

'La La Land' (musical)

'The Dark Knight' (superhero)

'Knocked Up' (comedy)

'Goodfellas' (gangster/crime)

'Insidious' (horror)