An aspect ratio is the measurement of an image expressed as a ratio of width to height.

This is usually written as 16:9 (16 units wide by 9 units high); or 1.78:1 (1.78 units wide by 1 unit high).

When films were first produced by Hollywood, they chose a 4:3 or 1.33:1 aspect ratio, which is pretty close to a square. All theaters at this time had square screens and nearly every film made prior to the 1950s was created in 1.33:1 ratio. For Disney, this included classics such as Snow White and Pinocchio.

 

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To combat the rise in home television popularity, Hollywood began making movies in a wider aspect ratio (2.55:1) to give moviegoers a reason to visit theaters again. Sleeping Beauty is an example of a film created using a 2.55:1 aspect ratio.

 

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Multiple formats were then used over the next 60 years, which suited a wide variety of television programming and studio films. However, until recently, televisions remained the same shape, making it difficult to display a movie created in a different aspect ratio than that of conventional televisions.

 

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Older square televisions used an aspect ratio of 4:3 or 1.33:1. New widescreen televisions use an aspect ratio of 16:9, or 1.78:1.

To fit a widescreen (1.78:1) movie onto a square TV, the image can either be cut into a square (below, left), or black bars can be added to the top and bottom to maintain the full picture (below, right).

This is an example of FULLSCREEN	This is an example of WIDESCREEN
To fit a fullscreen 4:3 or 1.33:1 movie onto a widescreen TV, the image may be stretched to fit the screen (below, left) or black bars can be added to the sides (below, right). Disney may still use the term "fullscreen" to describe the image on the right, even though it does not fill the entire screen.
Some movies are so wide that they need black bars even on a widescreen television (below, left). Disney still uses the term "widescreen" to describe this image, even though it does not fill the screen. Viewing a movie created in a very wide aspect ratio (like Sleeping Beauty in 2.55:1) on a square television will result in large bars on the top and bottom. (below, right)