In 1924, Erich von Stroheim attempted a literal adaptation of Frank Norris's novel McTeague with his moving picture Greed, and the resulting film was 9½ hours long. It was cut, at studio insistence, to four hours, then without Stroheim's input, cut again to around two hours. The end result was a film that was largely incoherent. Since that time, few directors have attempted to put everything in a novel into a film. Therefore, elision is all but essential.
However, in some cases, film adaptations also interpolate scenes or invent characters. This is especially true when a novel is part of a literary saga. Incidents or quotations from later or earlier novels will be inserted into a single film. Additionally, and far more controversially, filmmakers will invent new characters or create stories that were not present in the source material at all. Given the anticipated audience for a film, the screenwriter, director, or movie studio may wish to increase character time or to invent new characters. For example, William J. Kennedy's Pulitzer Prize-winning novel Ironweed included a short appearance by a prostitute named Helen. Because the film studio anticipated a female audience for the film and had Meryl Streep for the role, Helen became a significant part of the film. However, characters are also sometimes invented to provide the narrative voice.
As Sergei Eisenstein pointed out in his landmark essay on Charles Dickens, films most readily adapt novels with externalities and physical description: they fare poorly when they attempt the modern novel and any fiction that has internal monologue or, worse, stream of consciousness. When source novels have exposition or digressions from the author's own voice, a film adaptation may create a commenting, chorus-like character to provide what could not be filmed otherwise. Thus, in the adaptation of John Fowles's The French Lieutenant's Woman, the director created a contemporary Englishman in a romance with a woman to offer up the ironic and scholarly voice that Fowles provided in the novel, and the film version of Laurence Sterne's "unfilmable" novel, Tristram Shandy had the main actor speak in his own voice, as an actor, to emulate the narrator's ironic and metafictional voice in the novel. Early on, filmmakers would rely upon voice-over for a main character's thoughts, but, while some films (e.g. Blade Runner) may self-consciously invoke the older era of film by the use of voice over, such devices have been used less and less with time.
There have been several nominees for non-plus ultra of inventive adaptation, including the Roland Joffe adaptation of The Scarlet Letter with explicit sex between Hester Prynn and the minister and Native American obscene puns into a major character and the film's villain. The Charlie Kaufman and "Donald Kaufman" penned Adaptation., credited as an adaptation of the novel The Orchid Thief, was an intentional satire and commentary on the process of film adaptation itself. All of these are cases of Nathaniel Hawthorne's point. The creators of the Gulliver's Travels miniseries interpolated a sanity trial to reflect the ongoing scholarly debate over whether or not Gulliver himself is sane at the conclusion of Book IV. In these cases, adaptation is a form of criticism and recreation, as well as translation.
Change in adaptation is essential and practically unavoidable, mandated both by the constraints of time and medium, but how much is always a balance. Some film theorists have argued that a director should be entirely unconcerned with the source, as a novel is a novel, while a film is a film, and the two works of art must be seen as separate entities. Since a transcription of a novel into film is impossible, even holding up a goal of "accuracy" is absurd. Others argue that what a film adaptation does is change to fit (literally, adapt), and the film must be accurate to either the effect (aesthetics) of a novel or the theme of the novel or the message of the novel and that the filmmaker must introduce changes where necessary to fit the demands of time and to maximize faithfulness along one of these axes.
In most cases of adaptation, the filmmakers are required to create visual identities (for example, a characters' costume or set decor) since they are not specified in the original material. In these cases, the influence of film-makers may go unrecognised because there is no comparison in the original material, and even though the new visual identities will affect narrative interpretation. Peter Jackson's adaptations of The Lord of the Rings trilogy and The Hobbit by author JRR Tolkien represent an unusual case because many visual and stylistic details were specified by Tolkien. For the Harry Potter film series, author JK Rowling was closely consulted by the film-makers and she provided production designer Stuart Craig with a map of Hogwarts' grounds, and also prevented director Alfonso Cuarón from adding a graveyard scene because the graveyard would appear elsewhere in a later novel.
An often overlooked aspect of film adaptation is the inclusion of sound and music. In a literary text, a specific sound effect can often be implied or specified by an event, but in the process of adaptation, the film-makers will have to determine specific sound characteristics which subliminally affects narrative interpretation. In some cases of adaptation, music may have been specified in the original material (usually diegetic music). In Stephenie Meyer's 2005 Twilight novel, the characters Edward Cullen and Bella Swan both listen to Debussy's Clair de lune and Edward composes the piece Bella's Lullaby for the character Bella Swan. While Clair de lune was a pre-existing piece of music, Bella's Lullaby was not and required original music to be composed for the 2008 movie adaptation. In the 2016 sci-fi film 2BR02B: To Be or Naught to Be adapted from the story by Kurt Vonnegut, the film-makers decided to abandon Vonnegut's choice of music, stating that they felt it only worked in his prose because it wasn't actually heard. In the filmmakers' test screenings, they found that Vonnegut's style of music confused audiences and detracted from narrative comprehension. The film's composer Leon Coward stated "You can try to be as true to Vonnegut’s material as possible, but at the end of the day also you’re working with the material that you as a team have generated, not just Vonnegut’s, and that’s what you’ve got to make work."
Films sometimes use plays as their sources. William Shakespeare has been called the most popular screenwriter in Hollywood. There are not only film versions of most of Shakespeare's works but also multiple versions of many of the plays. Numerous spinoffs adapt Shakespeare's plays very loosely (such as West Side Story, Kiss Me, Kate, The Lion King, O, and 10 Things I Hate about You. Adaptations in languages other than English flourish around the globe, such as Akira Kurosawa's two epic films Throne of Blood (1957) and Ran (1985), and Éric Rohmer's Conte d'hiver (A Tale of Winter, 1992).
Similarly, hit Broadway plays are frequently adapted, whether from musicals or dramas. On one hand, theatrical adaptation does not involve as many interpolations or elisions as novel adaptation, but on the other, the demands of scenery and possibilities of motion frequently entail changes from one medium to the other. Film critics will often mention if an adapted play has a static camera or emulates a proscenium arch. Laurence Olivier consciously imitated the arch with his Henry V (1944), having the camera begin to move and to use color stock after the prologue, indicating the passage from physical to imaginative space. Sometimes, the adaptive process can continue after one translation. Mel Brooks' The Producers was a film that was adapted into a Broadway musical and then adapted again into a film.
Feature films are occasionally created from television series or television segments. In these cases, the film will either offer a longer storyline than the usual television program's format or will offer expanded production values. In the adaptation of The X-Files to film, for example, greater effects and a longer plotline were involved. Additionally, adaptations of television shows will offer the viewer the opportunity to see the television show's characters without broadcast restrictions. These additions (nudity, profanity, explicit drug use, and explicit violence) are only rarely a featured adaptive addition (film versions of "procedurals" such as Miami Vice are most inclined to such additions as featured adaptations) – South Park: Bigger, Longer & Uncut is a notable example of a film being more explicit than its parent TV series.
At the same time, some theatrically released films are adaptations of television miniseries events. When national film boards and state-controlled television networks co-exist, filmmakers can sometimes create very long films for television that they may adapt solely for time for theatrical release. Both Ingmar Bergman (notably with Fanny and Alexander but with other films as well) and Lars von Trier have created long television films that they then recut for international distribution.
Even segments of television series have been adapted into feature films. The American television variety show Saturday Night Live has been the origin of a number of films, beginning with The Blues Brothers, which began as a one-off performance by Dan Aykroyd and John Belushi. Mr. Bean was adapted into Bean and the sequel, Mr. Bean's Holiday.
Radio narratives have also provided the basis of film adaptation. The Hitchhiker's Guide to the Galaxy, for example, began as a radio series for the BBC and then became a novel that was adapted to film. In the heyday of radio, radio segments, like television segments today, translated to film on several occasions, usually as shorts. Dialog-heavy stories and fantastic stories from radio also adapted to film (e.g. Fibber McGee and Molly and The Life of Riley).
Comic book characters, particularly superheroes, have long been adapted into film, beginning in the 1940s with Saturday movie serials aimed at children. Superman (1978) and Batman (1989) are two later successful movie adaptations of famous comic book characters. In the early 2000s, blockbusters such as X-Men (2000) and Spider-Man (2002) have led to dozens of superhero films. The success of these films has also led to other comic books not necessarily about superheroes being adapted for the big screen, such as Ghost World (2001), From Hell (2001), American Splendor (2003), Sin City (2005), 300 (2007), Wanted (2008), and Whiteout (2009).
The adaptation process for comics is different from that of novels. Many successful comic book series last for several decades and have featured several variations of the characters in that time. Films based on such series usually try to capture the back story and “spirit” of the character instead of adapting a particular storyline. Occasionally, aspects of the characters and their origins are simplified or modernized.
Self-contained graphic novels, and miniseries many of which do not feature superheroes, can be adapted more directly, such as in the case of Road to Perdition (2002) or V for Vendetta (2006). In particular, Robert Rodriguez did not use a screenplay for Sin City but utilized actual panels from writer/artist Frank Miller's series as storyboards to create what Rodriguez regards as a "translation" rather than an adaptation.
Furthermore, some films based on long-running franchises use particular story lines from the franchise as a basis for a plot. The second X-Men film was loosely based on the graphic novel X-Men: God Loves, Man Kills and the third film on the storyline "The Dark Phoenix Saga". Spider-Man 2 was based on the storyline "Spider-Man No More!" Likewise, Batman Begins owes many of its elements to Miller's "Batman: Year One" and the film's sequel, The Dark Knight, uses subplots from Batman: The Long Halloween.
Video games have also been adapted into films, beginning in the early 1980s, although films closely related to the computer and video game industries had been done previously, such as Tron and The Wizard, but only after the release of several films based on well-known brands has this genre become recognized in its own right.
Similar to comic book-based films in the past, Films based on video games tend to carry a reputation of lackluster quality and receive negative reaction from both film critics or fans of the games on which they are based. However, a number of films have become successful with general audiences (such as Mortal Kombat, Lara Croft: Tomb Raider, Silent Hill, Resident Evil, and Prince of Persia) but all critical reception of the films are either mixed to poor.
However, some such as Super Mario Bros. were not as well received. The aforementioned adaptation was often criticized for being too dark in comparison to the popular video game series. Many anime Original Video Animations (OVAs) based on popular games have been released such as Dead Space: Downfall, Halo Legends, Dante's Inferno: An Animated Epic, and numerous films based on the video game series Pokémon.
The main cause of failure among video game adaptations is often cited as the genre's tendency for its films to drastically differ from source material, as producers, writers, and directors take many artistic liberties with the original games. Some notable examples include Doom, which traded in religious elements of the video games for scientific plot elements and openly parodied the game's first-person shooter gameplay. Silent Hill radically altered the backstory of the game, replacing the game's demonic cult which sought to birth a new god with a pseudo-Christian witch-burning cult. While still a comedic feature, the setting of the film adaptation of Super Mario Bros. was radically changed from a light, cartoonish kingdom to that of a dystopian city similar to the worlds of Blade Runner or Total Recall. The film also made several major alterations to the storyline from the game series, including the exclusion of series regular Princess "Peach" Toadstool, turning the villain Bowser into a human character named King Koopa (despite the character being a large, tortoise-like creature in the games), and making the titular brothers into father/son figures, explaining that Mario raised a much younger Luigi, unlike the game series.
Among the most well-known video-game filmmakers is Uwe Boll, a German writer, director, and producer who has become notorious among video-game fans and critics alike for making video games adaptations such as House of the Dead, Alone in the Dark, BloodRayne, In the Name of the King: A Dungeon Siege Tale, Postal, and Far Cry, all of which were almost universally panned by audiences and film critics for their deviation from the source material and simply bad quality. Boll is often compared to cult filmmaker Ed Wood, who created such films as Plan 9 from Outer Space and Glen or Glenda.
Another likely reason for the failure if video game adaptations is that structural conversion from video game to film format can be challenging for filmmakers. As Nintendo video game designer, Shigeru Miyamoto said in a 2007 interview:
“I think that part of the problem with translating games to movies is that the structure of what makes a good game is very different from the structure of what makes a good movie. Movies are a much more passive medium, where the movie itself is telling a story and you, as the viewer, are relaxing and taking that in passively. Whereas video games are a much more active medium where you are playing along with the story. In some cases, you are progressing the story yourself, or perhaps you get to a point where it gets too difficult and maybe you give up. I think that people who like movies also have an interest in the creative work that goes into making a video game. So there is interactivity with the video game that you don’t necessarily have with a movie. In that sense, I think the structures of the two are very different and you have to take that into account when converting a video game into a movie. I think that video games, as a whole, have a very simple flow in terms of what’s going on in the game. We make that flow entertaining by implementing many different elements to the video game to keep the player entertained. Movies have much more complex stories, or flow, to them, but the elements that affect that flow are limited in number. So I think that because these surrounding elements in these two different mediums vary so greatly, when you fail to take that into account then you run into problems.”
In an interview with Fortune in August 2015, Miyamoto has explained that Nintendo is planned to become an entertainment company rather than just the focus of game development, which includes potential partnerships with different studios that will be seen oversees by Nintendo’s Software Planning & Development (SPD) Division. As Miyamoto said:
“We’ve had, over the years, a number of people who have come to us and said ‘Why don’t we make a movie together—or we make a movie and you make a game and we’ll release them at the same time?’ Because games and movies seem like similar mediums, people’s natural expectation is we want to take our games and turn them into movies. … I’ve always felt video games, being an interactive medium, and movies, being a passive medium, mean the two are quite different.”
“As we look more broadly at what is Nintendo’s role as an entertainment company, we’re starting to think more and more about how movies can fit in with that—and we’ll potentially be looking at things like movies in the future,”
When a film's screenplay is original, it can also be the source of derivative works such as novels and plays. For example, movie studios will commission novelizations of their popular titles or sell the rights to their titles to publishing houses. These novelized films will frequently be written on assignment and sometimes written by authors who have only an early script as their source. Consequently, novelizations are quite often changed from the films as they appear in theaters.
Novelization can build up characters and incidents for commercial reasons (e.g. to market a card or computer game, to promote the publisher's "saga" of novels, or to create continuity between films in a series)
There have been instances of novelists who have worked from their own screenplays to create novels at nearly the same time as a film. Both Arthur C. Clarke, with 2001: A Space Odyssey, and Graham Greene, with The Third Man, have worked from their own film ideas to a novel form (although the novel version of The Third Man was written more to aid in the development of the screenplay than for the purposes of being released as a novel). Both John Sayles and Ingmar Bergman write their film ideas as novels before they begin producing them as films, although neither director has allowed these prose treatments to be published.
Finally, films have inspired and been adapted into plays. John Waters's films have been successfully mounted as plays; both Hairspray and Cry-Baby have been adapted, and other films have spurred subsequent theatrical adaptations. Spamalot is a Broadway play based on Monty Python films. In a rare case of a film being adapted from a stage musical adaptation of a film, in 2005, the film adaptation of the stage musical based on Mel Brooks' classic comedy film The Producers was released.