A dream sequence is a technique used in storytelling, particularly in television and film, to set apart a brief interlude from the main story. The interlude may consist of a flashback, a flashforward, a fantasy, a vision, a dream, or some other element.
Purposes
Commonly, dream sequences appear in many films to shed light on the psychical process of the dreaming character or give the audience a glimpse into the character's past. For instance, in Pee-wee's Big Adventure, the purpose of Pee-wee's dreams is to inform the audience of his anxieties and fears after losing his bike. Other times major action takes place in dreams, allowing the filmmaker to explore infinite possibilities, as Michel Gondry demonstrates in The Science of Sleep. Harvard psychologist Deirdre Barrett points out in the book The Committee of Sleep that, while the main content of dream sequences is determined by the film's overall plot, visual details often reflect the individual dream experience of the screenwriter or director. For Hitchcock's Spellbound, Salvador Dalí designed sharply angled sets inspired by his own dream space. Ingmar Bergman lit dream sequences in several films with a harsh glare of light which he says reflects his own nightmares (though most peoples have dim light), and Orson Welles designed a scene of The Trial to reflect the manner in which architecture constantly changed in his dreams.
Films normally present dreams as a visually accessible or objectively observed space, a discrete environment in which characters exist and interact as they do in the world rather than restricting themselves to the subjective point of view a dream is normally experienced from in real life. In this way films succeed in presenting a coherent dreamed world alongside the diegetic reality of the film. Via transition from one to the next, a film establishes not only the boundaries but resonances between the two worlds. These resonances can reveal a character's subjective observations or desires without breaking away from the objective viewpoint of the narrator, camera, or director with which some theorists, such as Christian Metz, believe the viewer identifies.
It is also possible to retroactively explain past plot elements as a dream sequence in order to maintain a plausible continuity in continuing fiction, such as a television series. Such was the case with Dallas, which had killed off Bobby Ewing, one of the more popular characters on the show; when the show's writers decided to bring Bobby back to the show, the tenth-season premiere "Return to Camelot" revealed that the events between Bobby's death and the end of season nine were all part of a nightmare his wife was having.
Techniques
Audio or visual elements, such as distinctive music or coloration, are frequently used to signify the beginning and end of a dream sequence in film. It has also become commonplace to distinguish a dream sequence from the rest of the film by showing a shot of a person in bed sleeping or about to go to sleep. Other films show a dream sequence followed by a character waking up in their own bed, such as the dream sequence George Gershwin composed for his film score to Delicious. In classic Hollywood, the wavy dissolve was the standard way to transition between reality and a dream; there would be a close-up of the character having the dream, which would begin shimmering as we crossed over from reality to fantasy. One of the most common contemporary transitions into a fantasy is to zoom in on a character's face and then spin around to the back of that character to reveal that he/she is now standing in an alternate reality.
The camera angles and movements used to depict dream sequences enable this kind of play and confusion between the diegetic reality and the dreamed world by presenting the dream world as a visually accessible space in which the character moves around the same as he does in the diegetic reality, as opposed to restricting themselves cinematographically to a subjective viewpoint even though dreams are generally understood to be experienced by the dreamer from their own subjective point of view. The first dream sequence in a film is more contested.