Citizen Kane made cinematic advances on many fronts, and its most significant contribution to cinematography came from the use of a technique known as deep focus. Deep focus refers to having everything in the frame, even the background, in focus at the same time, as opposed to having only the people and things in the foreground in focus. The deep focus technique requires the cinematographer to combine lighting, composition, and type of camera lens to produce the desired effect. With deep focus, a filmmaker can showcase overlapping actions, and mise-en-scène (the physical environment in which a film takes place) becomes more critical. Effectively manipulating the mise-en-scène for deep focus actively engages the whole space of the frame without leaving the viewer confused. Deep focus is most effective in scenes that depict Kane’s loss of control and his personal isolation because it gives the audience a clear view of the space Kane commands as well as the space over which he has no power. Gregg Toland, the cinematographer Welles chose for Citizen Kane, had used the technique in an earlier film he had worked on, The Long Voyage Home, but Citizen Kane marked the first time it was used so extensively or effectively. Citizen Kane introduced Hollywood to the creative potential of other cinematic techniques as well. One such innovation was a technique known as the "wipe," where one image is "wiped" off the screen by another. Other innovations involved unique experiments with camera angles.
Welles’s chosen Mercury Theatre cast was an asset to the film and vital to the success of techniques like deep focus. These cast members were classically trained theatrical actors, and none had ever made a movie before Welles brought them to Hollywood. Their stage training, rather than being overpowering, helped them to place themselves firmly in each scene, which complements the use of deep focus. The cinematography and acting technique combined so perfectly that the total control Welles was given over casting was justified. The combination of innovative techniques, not one individual technique, is what makes Citizen Kane such a cinematically important film.
Citizen Kane employs creative storytelling techniques as well. Acting almost as a biopic (biographical film), Citizen Kane portrays a long period of time realistically, allowing the characters to age as the story goes on. Instead of being told in a linear, completely chronological manner, Kane’s story unfolds in overlapping segments that add more information as each narrator adds his or her story. Telling Kane’s life story entirely in flashbacks was another innovative approach to storytelling. Flashbacks had been used in earlier films, but Citizen Kane used them most effectively. The flashbacks are given from the perspectives of characters who are aging or forgetful, which casts doubt on the memories being discussed. In other words, these are unreliable narrators whose own opinions and interpretations affect their accuracy. The storytelling techniques succeed in painting Charles Foster Kane as an enigma, a tortured, complicated man who, in the end, leaves viewers with more questions than answers and inevitably invokes sympathy rather than contempt.
Welles's achievements in this film marked a new direction in cinema. Many critics argue that Citizen Kane, with itsinventive use of lighting and shadow, is the first film noir, or at least the direct predecessor of noir, a genre that employs dark, moody atmosphere to augment the often violent or mysterious events taking place. Citizen Kane introduced Hollywood to the creative potential of cinematic technique. Even apart from the controversy the film stirred, a multitude of innovations made Citizen Kane the most exciting movie in the history of cinema at that time.