What Is an Aspect Ratio and Why Is It Important?

The shape of the image doesn't always match the shape of your TV screen

LG UH6500 4K UHD TV with TV and Movie Aspect Ratio Chart

LG and Wikimedia Commons (Public Domain)

When it comes to buying a new TV, there's no shortage of options to choose from. It's not just the wealth of features, brands, and sizes, there's also more technical details to mull over‚ such as aspect ratio. What exactly is a 16x9 or 4x3 aspect ratio, and why does it matter?

What Is the Screen Aspect Ratio?

Screen Aspect Ratio refers to the horizontal width of a TV or projection screen in relation to it its vertical height.

For example, most older analog CRT TVs (some are still in use) have a screen aspect ratio of 4x3, which gives them more of a squarish appearance. What the 4x3 reference means is that for every 4 units in width, there are 3 units of height.

Since the introduction of HDTV (and now 4K Ultra HD TV), aspect ratios have been standardized with a 16x9 aspect ratio. That means that for every 16 units in horizontal screen width, the screen has 9 units of screen height.

In cinematic terms, these ratios are expressed in the following manner: 4x3 is referred to as a 1.33:1 aspect ratio, while 16x9 is expressed as a 1.78:1 aspect ratio.

How Does Aspect Ratio Compare to Diagonal Screen Size?

TV sizes are most often measured by their diagonal screen length. As such, it's important to consider how a television's diagonal measurement would translate to its aspect ratio.

Here are some common diagonal screen sizes for TVs, translated into their screen width and height:

These measurements offer a general idea of how much space a TV will consume, but they exclude the frame, bezel, and stand.

Diagonal (inches) Width (inches) Height (inches)
32 27.9 15.7
40 34.9 19.6
43 37.5 21.1
48 41.7 23.5
50 43.6 24.5
55 47.9 27.0
60 52.3 29.4
65 56.7 31.9
70 61.0 34.3
75 65.2 36.7
80 69.6 39.1

Aspect Ratios and TV/Movie Content

With LED/LCD, OLED, and Plasma TVs, the consumer needs to understand the 16x9 screen aspect ratio.

TVs with a 16x9 screen aspect ratio are more suited to the increasing amount of 16x9 widescreen programming available on Ultra HD Blu-ray, Blu-ray, DVD, and HDTV broadcasts. However, there are still some consumers more used to the older 4x3-shaped screen.

Unfortunately, due to the increased amount of widescreen programming, owners of older 4x3 TVs are watching a growing number of TV programs and DVD movies with black bars on the top and bottom of their screens (commonly known as letterboxing).

Viewers not accustomed to this think that they are being cheated by not having the entire TV screen filled with an image. This is not the case.

Although 16x9 is now the most common aspect ratio you will encounter for home TV viewing, there are many other aspect ratios that are used in both home theater viewing, commercial cinema presentation, and computer graphics display.

Most films made after 1953 were (and continue to be) filmed in various widescreen formats, such as Cinemascope, Panavision, Vista-Vision, Technirama, Cinerama, or other widescreen film formats.

How Widescreen Movies Are Shown On 4x3 TVs

To fit widescreen films on a 4x3 TV, content is often re-edited in a Pan-and-Scan format, with the attempt to include as much as the original image as possible.

To illustrate this, imagine a film where two characters are talking to each other but from opposite sides of a widescreen image. If shown full screen on a 4x3 TV without editing, all the viewer would see is the empty space between the characters. Editors work around this problem by recutting the scene, jumping the shot from one character to the other as each one speaks. In this scenario, the artistic intent of the director is compromised. The viewer does not get enjoy the scene as it was intended; the facial expressions, body language, and set pieces between the two characters are scaled back or erased entirely.

Pan-and-Scan processing can also lessen the impact of action scenes. In the original 1959 widescreen version of Ben Hur, the entire chariot race scene is seen in full reach. In the Pan-and-Scan version, sometimes broadcast on TV, all you see is the camera cutting to close-ups of the horses and reins. All the other content in the original frame is totally missing, as well as the body expressions of the chariot riders.

The Practical Side of 16x9 Aspect Ratio TVs

With the advent of DVD, Blu-ray, and the switchover from analog to DTV and HDTV broadcasting, TVs with screens more closely shaped to that of a theatrical movie screen are better suited for TV viewing.

Although the 16x9 aspect ratio may be best for watching movie content, almost all network TV has benefited from the change. Sporting events, such as football or soccer, are well suited for this format. Now you can see all or most of the field in a single shot— and at a closer vantage point than the distant wide shots we're used to.

16x9 TV, DVD, and Blu-ray

Most DVD or Blu-ray Disc are formatted for widescreen viewing. On DVD packaging you may notice the terms Anamorphic or Enhanced For 16x9 Televisions on the packaging.

This means the disc image has been horizontally squeezed into a format that, when played on a 16x9 TV, is detected and stretched back out horizontally. This process maintains the original widescreen proportions so that the image is displayed in the correct aspect ratio without shape distortion.

If a widescreen image is shown on a standard 4x3 television, it is shown in a letterboxed format, in which there are black bars at the top and bottom of the image.

What About All Those Older 4x3 Movies and TV Programming

When viewing older movies or TV programs on a 16x9 aspect ratio TV, the image is centered on the screen and black bars appear on the sides of the screen as there is no image to be reproduced.

Pillarbox Image Example
Pillarbox Image Example. Robert Silva for Lifewire

In this scenario, you are still seeing the entire image on the screen, but the TV now has a wider screen width, and older content does not have any information to fill the entire screen.

Due to the various aspect ratios used in movie production, even on a 16x9 TV viewers may encounter black bars, this time on the top and bottom of the image.

BLACK-BARS.jpg
Robert Silva for Lifewire