Since the filming times were so long, everybody on the set tried their best to avoid any mistakes. At one point in the movie, the camera dolly ran over and broke a cameraman's foot, but to keep filming, he was gagged and dragged off. Another time, a woman puts her glass down but misses the table. A stagehand had to rush up and catch it before the glass hit the ground. Both parts are used in the final cut.
The film was shot in ten takes, ranging from four-and-a-half to just over ten minutes (the maximum amount of film that a camera magazine or projector reel could hold) duration. At the end of the takes, the film alternates between having the camera zoom into a dark object, totally blacking out the lens/screen, and making a conventional cut. However, the second edit, ostensibly one of the conventional ones, was clearly staged and shot to block the camera, but the all-black frames were left out of the final print. Most of the props, and even some of the apartment set's walls, were on casters and the crew had to wheel them out of the way and back into position as the camera moved around the set.
Although the film lasts about 80 minutes and is supposed to be in "real time", the time frame it covers is actually longer - a little more than 100 minutes. This is accomplished by speeding up the action: the formal dinner lasts only 20 minutes, the sun sets too quickly and so on. The September 2002 issue of Scientific American contains a complete analysis of this technique (and the effect it has on the viewers, who actually feel as if they watched a 100-minutes movie).
The picture was filmed entirely in-studio (except for the opening credits). The clouds that you see out the window are made out of fiberglass. For the effect of a police siren coming towards the apartment building at the end, Alfred Hitchcock had an ambulance come at full speed, from several blocks away, straight to the Warner Brothers studio, siren blaring all the way. The sounds were picked up by a microphone suspended from the studio gate.
This was the only movie James Stewart made with Alfred Hitchcock that he did not like. Stewart later admitted he felt he was badly miscast as the professor (he makes his first entrance 28 minutes into the film).
Story was very loosely based on the real-life murder committed by University of Chicago students Nathan Leopold and Richard Loeb, which was also the (fictionalized) subject of Compulsion (1959) and Swoon (1992).
The theatrical trailer features footage shot specifically for the advertisement that takes place before the beginning of the movie. David (the victim) sits on a park bench and speaks with Janet before leaving to meet Brandon and Phillip. James Stewart narrates the sequence, noting that's the last time Janet and the audience would see him alive.
The screenwriter Arthur Laurents claimed that originally Alfred Hitchcock assured him the movie wouldn't show the opening murder itself, therefore creating doubt as to whether the two leading characters actually committed murder and whether the trunk had a corpse inside.
Alfred Hitchcock's inspiration for the long takes came from a BBC Television broadcast of Rope (1939). The producer, Dallas Bower, decided on the technique in order to keep the murder chest constantly in shot.
Alfred Hitchcock's Rope (1948) is very different from Patrick Hamilton's play of the same name, although the basic plot is followed rather faithfully. Hitchcock made his own adaptation with Hume Cronyn and they created new dialogue and characters for their adaptation. In the play, there is no Janet Walker, no Mrs. Wilson, no Kenneth Lawrence, and no Mrs. Atwater. The play takes place in England. Brandon Shaw is Wyndham Brandon and Philip Morgan is Charles Granillo in the play. In the play, Rupert Cadell is only 29 years old and he is the current teacher of only Wyndham Brandon and Charles Granillo. In the film, Rupert looks like he is at least around the age of mid 40s. Rupert had been the teacher of Brandon Shaw, Philip Morgan, Kenneth Lawrence, and David Kentley. In the film, Rupert is currently a publisher.
Contrary to popular belief and Alfred Hitchcock's own claims in later interviews, there are several conventional edits during the movie: when Janet arrives at the party; when Phillip shouts "That's a lie!"; when Mrs. Wilson enters the room to announce the telephone call from David's mother; and when Brandon reaches into his pocket for his gun while Rupert narrates his theory on how the murder was committed. Some add the cut from the shot of the apartment's exterior (with the opening titles superimposed over it) to its interior at the beginning, but that one does not genuinely contradict the claim that the film is made to simulate a single continuous take any more than the cut to the end credits does.
DIRECTOR_CAMEO(Alfred Hitchcock): appears, though barely if at all recognizable, walking down the street during the opening credits. His profile also appears on a neon sign visible through the apartment window approximately 55 minutes into the movie. The neon sign advertises "Reduco", the same fictional weight-loss product that Hitchcock advertised in his famous newspaper ad cameo in Lifeboat (1944).
Alfred Hitchcock made an opening romantic scene in Central Park with Joan Chandler (Janet Walker) and Dick Hogan (David Kentley). The scene was used for the 1948 promotional trailer but deleted in the film.
The star signs that Mrs. Atwater states for the movie actors she discusses are in each case correct: James Mason really was a Taurus, Cary Grant a Capricorn, and Ingrid Bergman a Virgo, just as she says.
The play, originally entitled "Rope" when it premiered in London, was re-titled "Rope's End" when it went to Broadway. The Broadway play "Rope's End" opened on Sept. 19, 1929 at the Theatre Masque (now called the John Golden Theatre) and ran for 100 performances.
With Hume Cronyn, Alfred Hitchcock made a very different Rupert Cadell for the film. In the play, Rupert Cadell is only 29 years old. Rupert Cadell in the play had an affair with one of his students. Rupert Cadell is the current teacher of only Wyndham Brandon (Brandon Shaw in the film) and Charles Granillo (Philip Morgan in the film) in the play. In the film, Rupert was the "past" teacher of Brandon Shaw, Philip Morgan, Kenneth Lawrence, and David Kentley. In the film, Rupert looks like he is at least in his mid 40s. In the film, Rupert is currently a publisher. In the film, Rupert Cadell has a romantic relationship with Mrs. Wilson. Rupert Cadell also has plans of marrying Mrs. Wilson in the future. But in the play, there is no Mrs. Wilson. Instead of Mrs. Wilson, there is a 35 year old french servant named Mr. Sabot.
Although Rope was based on the play by Patrick Hamilton, still it may have been also based on an incident that happened in Alfred Hitchcock's life. There was an assassination scene in Hitchcock's film Foreign Correspondent (1940), Hitchock heard that this assassination scene was copied in real life to kill someone at a place called Tarahan. This incident was mentioned by Alfred Hitchcock in Tomorrow Coast to Coast (1973).