1.  The video aspect ratio of a video image refers to its width and height proprtions. (W:H)
  2.  The two popular video aspect ratios are the 16:9 and 4:3 (16 by 9 and 4 by 3)
16:9 Aspect Ratio

16:9 Aspect Ratio

Aspect Ratio 4 : 3

Aspect Ratio 4 : 3

  1. Generally speaking standard definition video is in the 4: 3 aspect ratio.
  2. It should also be noted that any movie made before 1953 employed the 4:3 aspect ratio.
  3. The 16:9 aspect ratio is the default for high-definition video.
  4.  16:9 is also referred to as the widescreen format. This means for every   16 units of vertical space taken up on the screen  there are 9 horizontal units.
  5.  Most HDTVs have the 16:9 aspect ratio.
  6.  Older non-HDTVs support only 4:3 video aspect ratio.
  7.  There’s also the 21:9 aspect ratio employed in cinemas for the screening of movies
  8.  The 14:10 aspect ratio is used for IMAX films which is supported only by a few cinemas.
  9. The 19:10 aspect ratio is specially used for IMAX Digital. Most IMAX theatres support this format.
  10.  When a movie made in the 21:9 aspect ratio is displayed on TV, the extra sapce is filled with black bars called letterboxes.
  11.  When a movie in the 4:3 aspect ratio is displayed in a widescreen 16:9 TV, black upright rectangles (pillars) are used to fill up the space to the left and right. These are called pillarboxes.