Watching some recent movies, it occurred to me that the use of "bluescreen" effects -- having characters play their scenes in front of a blank screen and then adding in the background digitally -- may prove to be to today's movies what rear projection was to movies from the '30s through the '60s: something that almost instantly dates a movie and makes it look kind of cheesy.
If you look at movies from the '20s, before rear projection was invented, a scene in a moving car is usually actually shot in a moving car. Even as late as 1931, after the coming of sound, The Public Enemy shot some scenes this way, and the scenes look terrific. And then in 1933, rear projection was invented, and was gradually adopted as a useful substitute for the difficulty and expense of sending the stars of a film to a location, or photographing them in an automobile or other vehicle. So in Hitchcock's Notorious, just about every other scene uses rear projection, because the second unit filmed a bunch of shots in Rio de Janeiro, and then Hitchcock projected those scenes behind Cary Grant and Ingrid Bergman in the studio in Hollywood.
By that time, while many European and Asian movies continued shooting "real" scenes in cars and on trains, Hollywood movies used rear-projection for pretty much any vehicular scene, even in the '50s when location shooting became much easier. It wasn't just about the difficulties of shooting, but about the desire of the old-guard studio people to control the conditions of shooting (lighting, sound, etc). One wonderful exception was Gun Crazy, where, for the big robbery sequence, directer Joseph H. Lewis stuck a camera and sound equipment in the back of a car and filmed the entire robbery and getaway in a single take.
The problem with rear projection is the same as the problem now with blue screen: it just doesn't look the same as the real thing. If the stars are actually in the car, driving along the street, then they look like they're at one with the setting, because they are. But if they're not really in a moving car, no matter how cleverly the process shot is pulled off, there's always a certain amount of disconnect between them and their environment: with rear-projection, the environment looks "flatter" than they do, and with today's process shots, you sort of get the feeling of flesh-and-blood humans in a digitized environment. Just as in an action scene, a CGI scene of someone jumping off a cliff is a poor substitute for having a real live stuntman jump off a cliff, putting actors in an artificial setting is a not-quite-convincing substitute for a real setting. I have a feeling that the process shots in today's movies will soon look as cheesy as anything from the '50s.
So I'll end this with a question: what's the worst back projection you've seen in a movie? There are so many choices, but one pick might be 1964's The Pleasure Seekers (aka Three Coins in the Fountain in their Underwear). They actually brought the cast over to Spain for this thing, yet half the scenes are filmed in front of back projection so obvious that you expect the Leaning Tower of Pisa to turn up by mistake in the background a la Police Squad! In fact, most of Fox's CinemaScope spectaculars -- particularly the ones by their star director, Jean Neuglesco -- have hilarious rear-projection; they spent all that money on location shooting, yet they always had to shoot their actors and actresses in a studio in front of a wobbly 'Scope plate.
Another candidate would be Ernest Lehman's 1972 film of Portnoy's Complaint, if only because almost nobody was using that kind of blatantly bad rear-projection by 1972 -- yet Lehman did, and it makes a 1972 movie look like it was filmed in another era. You haven't lived till you've heard Karen Black say "fuck" in a movie that otherwise looks like a scene out of a 1956 Fox chick-flick.