The most significant contribution of Citizen Kane 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.