I think that the rise of widescreen DVDs may have influenced the movie business in a particular way: these days, many films -- perhaps even a majority of films -- are shot in the 2.35:1 'Scope format instead of the alternative "flat" format (1.85:1 ratio). In the '80s and '90s, 'Scope was mostly used for big action blockbusters; now it's used more and more for comedies, dramas, even kids' movies. Also, in the '80s, most 'Scope movies didn't make particularly elaborate use of the wide frame, in part because filmmakers knew that the frame would be chopped in half when the film was released on VHS. Now there are more filmmakers who use the whole frame in imaginative ways (Wes Anderson is an example). I think the comeback of 'Scope might have something to do with the fact that the filmmakers know that their compositions will be preserved intact on home video.
Anyway, that's dangerously close to a current topic, so I'll switch to talking about something old. When I see a 'Scope film in widescreen for the first time after years of watching it in pan-and-scan, it's often surprising how different it can be, how the original compositions reveal details and even story points that changes the way the film comes off. My favourite example is from Gigi (directed by Vincente Minnelli, who adapted brilliantly to CinemaScope -- his preference for long takes made him a natural for the new format, since it allowed him to get even more characters in the same frame without having to cut). In the "Thank Heaven For Little Girls" number near the beginning of the film, Honore (Maurice Chevalier) sits at the left of the frame; a little girl in white is in the middle of the frame, and next to the girl, at the right of the frame, is a beautiful young woman dressed in white like the little girl. Honore sings the famous/infamous lyrics:
Thank heaven for little girls,
For little girls get bigger ev'ry day.
Thank heaven for little girls,
They grow up in the most delightful way.
The picture of the little girl next to the grown woman illustrates what the song is about: the little girl will grow up to be a beautiful woman who will captivate men (and, as Gigi discovers, be expected to sell herself to men). But when the film is shown in pan-and-scan, the only characters visible in the shot are Honore and the little girl; the woman, the grown-up version of the little girl, is not seen. Which means that people watching this number on TV get the impression that it's a hymn to pedophilia or something. The pan-and-scan format wrecks the shot, the song, and gets the film off on the wrong foot.
On the other hand, there are some '50s films that arguably work better in pan-and-scan. A lot of Twentieth-Century Fox movies fall into this category. Fox, which introduced CinemaScope, idiotically insisted that all its movies be shot in widescreen (they stuck to this policy until the late '60s at least). This meant that filmmakers who had no particular aptitude or liking for widescreen composition were forced to use the huge 'Scope screen even if they had nothing with which to fill the frame. Which means that a lot of Fox movies from this era are essentially 1.33:1 movies put into a 2.35:1 frame; the directors compose the shots the way they always did, with two characters in the middle of the frame, and then there's a lot of empty space around them. A lot of Leo McCarey's An Affair to Remember is like this. Other directors just became determined to fill that screen come what may, so they would have characters talking to each other from opposite sides of the frame, conveying the impression that they were not so much interacting as hollering to one another from twin peaks in the Alps. I recall Nunnally Johnson's The Three Faces of Eve being like this; Eve (Joanne Woodward, who won an Oscar) on one end of the frame, her psychiatrist on the other. When a film like this is panned and scanned, shots like these are broken up into two, cutting back and forth between characters who were originally in the same frame -- and that actually makes the composition and staging look more normal, because it's probably the kind of composition that the director wanted to have in the first place.
I'm not actually saying that movies like these should be panned and scanned; 'Scope movies should be shown in their original format, period. I'm just saying, I guess, that seeing movies like these in their original format can often shed cruel light on just how badly the directors adapted to that format. As somebody once said (the quote has been attributed to many people, including Fritz Lang), the only thing CinemaScope is really good for is photographing funerals and snakes.