What is the aspect ratio

 The aspect ratio describes how the picture appears on the screen. Take 4:3 as an example, 4 refers to the width and 3 refers to the height. To understand this question, we have to look back at history.

The size of the first movie film used by Edison in the laboratory was 1 inch wide and 0.75 inches high. To avoid decimals, it became the most familiar 4:3 format, which lasted 60 years as the standard format for film production.

Then came a watershed moment in American history: the television boom. For a while, the 4:3 aspect ratio of movies worked well with rectangular television screens, and seeing more and more households buying televisions, studios had to use the new format in an attempt to draw audiences away from home back to the theater. Before understanding the widescreen, let us get familiar with CinemaScope, Panavision and widescreen. These three words can be translated as widescreen, but they are not exactly the same. Widescreen is a general term, and Cinema-Scope is the name of a wide-screen system and a trademark. The width of the screen is about 2.5 times the height. From the 1970s, this widescreen format became (and trademarked) Panavision, and thus 2.35:1 was born. It should be pointed out that not all movies shot with Panavision are widescreen.

If the director had shot the film with a CinemaScope or Panavision camera with a wide lens, the frame would have been compressed onto 35mm film stock, the same kind Edison used. In the movie theater, the picture is restored to its normal form, and this process sometimes causes the image to be distorted, which we call anamorphic distortion. This phenomenon also occurs when making DVDs, but the advantage is that the viewer sees the same picture as in a movie theater.

Transplanting the cinema to the home means squeezing the widescreen onto an ordinary TV screen. Since the width of the widescreen is 2.35 times the height and  the TV is 1.33 times, post-production equipment is required to complete this conversion work. The preparation process for release is called "Pan & scan". Technicians focus on what happens when the action or dialogue occurs, cutting out what doesn't fit on the TV screen. Directors and movie fans are not keen on "Pan & scan", because it seriously changes the structure of the screen during shooting, and what the audience sees is no longer the director's true intention. There is a similar problem for another aspect ratio of 1.85:1.

1.85:1 is between pure widescreen and "Pan & scan", looks a lot like Panavision, but without the extra cost of lens and anamorphic production. Unlike "Pan & scan" which cuts off parts of the original frame, 1.85:1 fills the screen by including the top and bottom of the movie frame, allowing you to see something that doesn't look like it.

So why not make a 2.35:1 widescreen TV? It is fantastic for movies, but just not worth it for regular TV with Panavision. Besides, if it did, the evening news would look like a distorting mirror, with some short and fat and some tall and thin.

The birth of high-definition television solved the problem. Mathematicians believe that the best compromise between these different standards is 1.77:1, which is commonly known as 16:9. Although it does not completely solve the problem, it is the most ideal method available. When a movie is released on DVD, the studio can use one aspect ratio, or offer both widescreen and Pan & scan versions on the same disc.