Conventions of Film Noire

Film Noire is a genre of films which became popular round the 20's. During this time, Film Noire films were made very cheap using minimal lighting, setting and characters. These sort of film became popular party because so many were produced, nearly all following the same structure: Detective, Deputy and a Femme Fatale.
The Detective: This was often the main character, he is often played by a gruff sounding male actor. The narrative is often told by this character.
The Deputy: This is often a disposable character - which leads on to more important plot devices. Though we'd assume this was an important part character, we will find that plot more focuses around on the more important, main detective.
The Femme Fatale: This is often the min female lead role,playing a sly and manipulative who manages to sway the detective to do what she wants him to. This happens though most the film with the detective unaware of this until near the end of the film, where she is discovered for what she is.

Film Noire films often have the detective searching for someone or something, if something, it is often a valuable stolen item

One of the most famous conventions for this the minimal lighting used. It is common that only two set lights are used. There are often used to only show one side of the face, this is used to set the dark tones which many Film Noire films contain. This is called low key lighting.

Another convention is the costumes of the main characters. The detective is seen wearing a trench coat and a hat. There is rarely a film of this genre which does not have this. This conveys mystery about the character.