It ticks me off that-

Just to update my friend wrfarley: simply put, the aspect ratio is the width of the screen vs. its height.

Thus, a 1.66:1 film is about one and one-third times as wide as it is "high". In practice, this is very little different from the so-called "standard" screen (or "fullscreen"), which means a movie shot at a ratio of 1.37:1. Thus, if you don't see a 1.66:1 film in widescreen, very little of the picture is cut from view.

Since, as wrf said, an old square TV screen is 1.33:1, the closer a film's aspect ratio to that size, the more of the film you see.

He was mistaken about a couple of details. CinemaScope was pioneered by 20th Century Fox in 1953 to lure people back to theaters from staying home watching television. It was not a company in itself (neither is VistaVision, a widescreen system developed by Paramount). 'Scope was never as wide as 2.66:1; its maximum width early on was 2.55:1, meaning the picture was more than 2 1/2 times wide as high. When they switched from optical to stereophonic sound in 1955, the CinemaScope image was refined to 2.35:1, which was and remains one of the industry's standard widescreen ratios.

The prevalent widescreen process is Panavision, which ultimately replaced CinemaScope in the late 60s, and which was originally shot at the same 2.35:1 a.r. However, as wrf says, 1.85:1 became the more common a.r. by the 70s, though many 2.35:1 films were and are made. There are or have been many other processes, most of them the exact same thing as CinemaScope or Panavision, just under different names. Some others, like Todd-AO or Cinerama, were used only sporadically and eventually faded out.

Cinerama premiered a year before CinemaScope but was used on only a few films, since it employed three cameras to shoot the full arc of a widescreen image. This looked great in a theater but when projected flat on a TV print (even in widescreen) the picture looks odd on the left and right sides, as if it were "folded" back. People and objects appear to come into view from back to front along the side of the picture, then literally become flat when face-on in the center image. You can even see two "creases" in the film, separating the left and right sides from the center, and although these have largely been removed in the latest DVDs, the "folded" image is still very evident. It's hard to explain, but if you ever see the film How the West Was Won watch how the sides are photographed and you'll see what I mean. In fact, Cinerama films had to be shot with the actors speaking not directly to one another but off to one another's sides, so that when projected it would appear they were talking face-to-face. A ridiculous and unsatisfactory process, in my opinion.

There are many different aspect ratios used: 1.66, 1.77, 1.85, 2.00, 2.20, 2.35, 2.55, 2.66 and others. Again, the lower the number, the less of the film that's lost when shown fullscreen on TV. When 'Scope films first hit television in the early 60s, they developed the so-called "pan and scan" process, by which a technician operating three cameras essentially reshoots the movie. Each camera records a portion of the original film -- on the right, left, and panning (moving from one side to another) in the center. This allows him to film a part of the original for a TV print that will fit into a television set's 1.33:1 frame. The technician chose what part of each scene he'd leave in and which he'd cut out.

The problem is that in doing this you're losing around half the picture (the part the technician decided not to record for the print), which means that you'd hear voices of people you don't see coming from the side, the action on one side of the film isn't seen, and so forth. Also, to re-photograph a widescreen film in fullscreen size, you have to zoom in closer to the original print, which means you pick up the grain of the film, making it somewhat blurry and losing its sharpness. The wider the film, the closer you have to zoom in to get a fullscreen image -- thus the more picture you lose and the grainier it becomes.

I grew up watching a lot of widescreen films in pan & scan TV prints and when I finally saw some of them widescreen in the 90s, what instantly struck me was not the width or seeing things I'd never seen before -- it was the sharpness and clarity of the picture, which is evident from the first moment. That's when I realized what I'd really been missing.

A film like Ben-Hur, for instance, shot very wide at 2.66:1 -- nearly two and two-thirds times wide as it is high -- becomes a grainy blur fullscreen, apart from the fact you're losing well over half the picture in each frame. The Great Escape has the identical problem.

On the other hand, Moby Dick -- which was shot in a modest widescreen aspect ratio, 1.66:1 -- suffers very little seen fullscreen. The so-called "black bars" seen at the top and bottom of widescreen films (so they can be shown in their complete and correct image) are barely visible on a film with an a.r. of only 1.66:1. In such cases, there was no need to have a technician use pan & scan or cut out half the picture the movie for the TV print: it was just photographed by a camera a bit closer to the image. Very little is lost, and very little of the grain is evident. But by 1.85:1, you do begin to lose some significant amount of picture and get a less sharp image than leaving it widescreen.

Two last things: you know the term "letterboxed", which means that a film is shown on a black background in its original widescreen format. The word comes from the oblong shape of a letter box. There is also a process called "windowbox", which is used mainly on 1.37:1 films. On a 1.33:1 TV, there is still a slight loss of picture around the edges even of a 1.37:1 film; windowboxing frames the film on all sides so that there are very slight black borders enclosing the entire picture, allowing you to see it in its entirety. Criterion does this with many of its films.

The other thing is, I never understood why widescreen DVDs carry the notation stating "The black bars at the top and bottom of your picture are normal" in describing what the film will look like on your television. The word "bars" makes it sound as if something is being blocked from view, when in fact you're seeing the entire picture, in contrast to a so-called "fullscreen" image. A lot of people objected to letterboxing when it first began because they were freaked out by the black top and bottom and thought the image was too small. They'd rather lose half the film than see it correctly. But this is becoming more widespread, even on TV shows, so most people now realize it's to their benefit.

It also makes more inexplicable Fox's decision to release most of the widescreen films it issues on its new Fox Cinema Archives MOD line in lousy pan & scan prints instead of in their original widescreen aspect ratios. No one does this any longer, and it's a real cheat on the consumer, especially since Fox originated the era of widescreen movies in 1953.

Sorry I went on so long! Didn't expect to.