What are the big differences between the Macbeth play and the 1971 film by Roman Polanski?
Polanski's 1971 Macbeth, which LA Times Critic David Ng describes as a "cinematic jolt," reflects the experimentation that characterized the era in which it was filmed (late 1960s and early 1970s). Notable changes from the play are as follows:
More blood and violence: Macbeth is a bloody play and the characters speak frequently about blood, which becomes a potent metaphor for guilt. However, the Shakespeare version keeps much of the actual murder and mayhem discreetly off-stage. For example, in the original play, King Duncan's death is noted after the fact. In Polanski's version, we actually witness the murder.
Nudity: Not only do we have Lady Macbeth's famous sleepwalking scene turned into a famous nude sleepwalking scene, the elderly, grotesque witches are shot in the nude.
Younger Macbeth and Lady Macbeth: Though generally understood as middle-aged, the Macbeths in the film version are deliberately made younger to appeal to a youthful audience: 26- and 23-year-olds play the title roles.
More pessimism: In Shakespeare's original, the rightful heir to the throne invades and restores order. We are shown clearly the disruptive results of Macbeth's ambition, murder, and tyranny. Polanski's view is darker: as film critic Roger Ebert put it, the movie's Macduff brings "workaday revenge" rather than "God's justice."
More focus on Macbeth's point of view: While the play shows us Macbeth's point of view, it also pulls away from a narrow focus on him to reveal a bigger picture: Hecate speaking to her witches, for example, or Macduff's point of view. Shakespeare thus places us in a wider moral universe where the competing agendas are clearer to the audience, adding to the dramatic irony.
It's also worth noting that many critics see in the bloodiness of Polanski's film a reflection of the brutal murder of his wife Sharon Tate by the Manson gang, which happened the year before he started filming the movie.
When I saw the movie, the most vivid differences were the sex and violence. Polanski puts lots of bloody violence on screen, including an amazing crossbow bolt to the forehead at one point. There's also more nudity in the film. (That's an understatement, since none of the stage versions I've seen had any.) Polanski in general anchors the film more, trusts the verse less. (He provides visual cues.) The pacing is different, with the visuals filling comparatively silent gaps.
One online commentator pointed out something I'd forgotten, namely that Polanski's Lady Macbeth didn't read the whole text of the crucial letter Macbeth sent her.
One thing that is added to the play which I think is really effective is the focus on the bear that is being baited, which is of course an important image in the play that Macbeth uses to describe his own situation at the end of the play. As #2 points out, the play is very bloody and sexual - things that are implicit perhaps in the play but really help us to understand the violence and "raw emotions" that are being revealed.
As far as I can tell, the main differences in Polanski's version is the portrayal of Lady Macbeth and the character of Ross. In Shakespeare's original, Ross is not an important character. Polanski's version really played him up and made him a real thug.