Aspect ratio

The aspect ratio of an image describes the proportional relationship between its width and its height.

• It is commonly expressed as two numbers separated by a colon. 
• For example, a 21:9 aspect ratio means that for a width of 21 units, the height must be 9 units.

Most televisions and computer monitors currently available have an aspect ratio of 16:9, which offers a perfect fit for high definition television shows.

Is a 21:9 TV Worth It?

A 21:9 TV is only worth it if you almost exclusively watch movies (more than 80% of the time). If you watch normal 16:9 content (like a HDTV channel) on it, you will see black bars on the sides.

This reduces the viewing area for 16:9 content considerably. A 58" 21:9 television corresponds to the same viewing area as a 47" TV for 16:9 content. 

Obtaining height, width, and area of the screen 

• Screen specifications are given by their diagonal length. 
• The following formulae can be used to find the height (h), width (w) and area (A), where r stands for ratio and d for diagonal length.

  

Visual comparisons

• When comparing two aspect ratios, one may compare images with equal height, equal width, equal diagonal, or equal area. 
• Televisions and other displays typically list their size by their diagonal. Given the same diagonal, a 4:3 screen has more area compared to 16:9.

For CRT-based technology, an aspect ratio that is closer to square is cheaper to manufacture. The same is true for projectors, cameras, camcorders, etc.

Black bars look like on TVs with different aspect ratios?

The position and size of black bars on television depend on two factors:

• The aspect ratio of television and the aspect ratio of the video we are watching. 
• Any mismatch between the two will be filled by the black color. This practice is called "letterboxing".

 The following picture shows the black bars for various televisions and aspect ratios (4:3, 16:9 and 21:9). All televisions have the same diagonal length.

Another example as, a group of images that all have an aspect ratio of 16:9, one image might be 16 inches wide and 9 inches high, another 16 centimeters wide and 9 centimeters high, and a third might be 8 yards wide and 4.5 yards high.

Applications and uses

1. Graphic / image 
2. Image aspect ratio 
3. Display aspect ratio: the aspect ratio for computer displays 
4. Paper size 
5. Standard photographic print sizes 
6. Motion picture film formats 
7. Standard ad size 
8. Pixel aspect ratio 
9. Photolithography