As part of English 408A, Media Writing at the University of Waterloo, I have been doing some extra reading regarding screenwriting. While movies are clearly a visual art, where they excel is clearly in the narrative performance. Due to the compressed length, a screenplay is far shorter, and thus the narrative must be compressed. This is one of the reason why many movie adaptations are so very different from the original novel. Complex subplots which stray from the main plot are cut loose, perhaps replaced with shorter subplots which provide a quicker payback. I've occasionally wondered exactly why it is that the short stories of Philip K. Dick are so frequently adapted by Hollywood. Blade Runner, starring Harrison Ford is a prime example, and is also a film classic. There are a number of themes from the novel which were dropped from the film. The most obvious of which is Mercerism, and the empathy boxes. The shared artificial reality, designed to allow users to share pain in a spiritual manner, can be read as a critique of our modern media culture. There's also an interesting parallel to the video screens in Fahrenheit 451. Dick was critical of modern media, in a way that wouldn't necessarily carry over into a commercial film.
Sadly, this and several other themes are left out of the film. In the case of Blade Runner, I think these changes were justified. Film emphasizes the visual, and while I believe that Philip K. Dick was an exceptionally visual writer, many of the themes in Do Androids Dream of Electric Sheep just wouldn't translate well into film. Where in a novel, the author can show the thoughts of the protagonist, where in film, this can only be achieved artificially, such as through a narrative voice over.
By trimming down these themes, Ridley Scott was able to emphasize those that remained, and to emphasize the new form of visuals. The world of Blade Runner is very different from that of the original novel. Where Dick's world was a post-nuclear wasteland, depopulated through emigration, the world shown in the film is a dark, densely populated melting pot of American and asian cultures. This visual style later came to embody the cyberpunk aesthetics.
It's interesting to consider some of the other adaptations of Dick's work, especially those from short stories. Where in Do Androids Dream of Electric Sheep? themes were removed from the screenplay, when adapting his short stories, the stories are fleshed out. Not every adaptation remains true to even the core plot of Dick's original story. Often, the main elements which remain include the name, those of the major characters, and the key plot point of the story. Others, like the Minority Report, follow the path of Blade Runner, weaving together many of the strands of the original narrative, keeping "mostly true" to the original tale, which in some ways, becomes a minority report of its own.