The question is not as simple to answer as one would think. The aspect ratio may seem random but in fact it isn’t. A lot of thought went into it and what we ended up with is a compromise.
The problem is that traditionally television sets worked on an aspect ratio of 4:3. A cinema screen on the other hand is much, much wider. Since movies are mainly produced for the cinema they use the full panoramic width available. This wouldn’t be a problem if we didn’t watch movies on television but we do. So how do we present a picture that is shot in cinemascope on a 4:3 screen?
There are two alternatives. You either cut off the edges or have massive black bars on top and bottom. Cutting off the sides with many movies simply doesn’t work – imagine a dialogue where you see none of the actors – that left us with the ugly black bars. If you grew up in the 80ies and had a smaller television set you what that means. With the massive black bars there was hardly anything left of your small TV set so the actual picture was tiny. Often one could hardly see anything. Changing the aspect ratio would have been an alternative but how you do that with millions and millions of TV sets out there that don’t have it.
First you have to convince the TV stations to broadcast in 16:9. As much as they were interested in the technology they wouldn’t change a thing until there was a demand. But how do you create demand if there are no programs? It was a catch 22.
When LED and Plasma technology became available it was a chance to finally succeed in changing from 4:3 to a widescreen format and as you can tell at this stage; it was a major success. But did we succeed?
Well; the original idea was to show movies without the black bars on top and bottom but obviously that wasn’t achieved with this format. Panavision or Cinemascope are using an aspect ratio of 2.2 / 2.35. The TV format of 16: 9 (1.78:1) is nowhere near that. Did we fail?
Well; not really. Speaking in practical terms; 22:1 isn’t realistic. There are a few reasons. Most obvious one is; TVs would have to be monstrous in order to accommodate that. That probably wouldn’t stop anyone but what about all the content that was created pre widescreen?
All old TV shows were produced for a TV audience and TV’s by default were 4:3. Stretching to fit a 22:1 screen is impossible. Losing all the old shows and TV series to accommodate modern widescreen television? No way!
A very clever man – Dr. Kerns H. Powers – looked at the problem of different formats and he came up with a solution. He looked at all the available formats at the time. He cut out rectangles with equal areas and aligned them at the center. He discovered that they all fit in a rectangle with an aspect ratio of 1.77:1 and not just the outer sides but there was also an inner side where a rectangle with that aspect ratio fitted. It is the mean between the two extremes 4:3 and 2.23:1. And guess what; 1.78:1 is the aspect ratio of a 16:9 television.
While this is a perfectly good explanation for the choice of format It doesn’t help if you only watch movies. Movies are still shot in Cinemascope or Panavision. Some manufactures therefore do not follow 16:9. Most famous for ultra wide screens is Philips. They advertise their new Ambilight in 21:9 aspect ratio. While this is very cool to watch movies it is less than ideal for regular programs. You want to be careful when buying a television. If it has an awkward format you may regret it later when watching programs in 16:9 or even 4:3.