Video Aspect Ratios

Traditional CRT televisions have a 4:3 aspect ratio where as newer LED, LCD and Plasma televisions use a 16:9 widescreen aspect ratio. This means that footage played back in various different aspect ratio's will vary depending on the television's format. On 4:3 televisions, a widescreen image is shown in 2 different ways, cropped or letterbox (see images below). The cropped method looses the visual image from either side of the footage, where as with the letterbox format, the image is displayed at a decreased resolution due to the black bars required at the top and bottom of the screen. Sometimes 16:9 footage can appear squashed to fit.

                          

 4:3 image with cropped sides  16:9 widescreen letterbox 16:9 squashed into 4:3

 

Widescreen LED, LCD and Plasma televisions have a 16:9 aspect ratio, in standard defenition (1024x576 pixels), enhanced definition (1366x720 pixels) and true high definition (1920x1080 pixels).  While newly created content is now 16:9 widescreen, older content was still produced in 4:3, so will be displayed with black bars on either side of the image. Occasionally you may have your 4:3 image stretched to 16:9 producing a distorted image. Modern televisions have display options that can correct these distortions, so that viewing is not hindered. 

       

       Widescreen 16:9 image display

       STD 4:3 displayed on 16:9 television             STD 4:3 stretched to 16:9

                                                    
          
It is worth noting that DVD's are are only standard definition (1024x576), where as Blu-ray is true high definition (1920x1080). However DVD & Blu-ray movies have different aspect ratio's, such as 1.85:1 or even 2.4:1.  This is because they are filmed for cinema screening, not television. When selecting a display option on your modern television you will see options such as cinema1, cinema2, etc, which will give you a better result.  These settings may zoom and crop the edges slightly, so you will need to select the best setting for the DVD or Blu-ray that you are playing. You will always have the letterbox option if you wish to see the full width of the screen, but black bars will appear top and bottom.

 

  
1.85:1 widescreen letterbox

On the back of DVD & Blu-ray covers, you will also see reference to 16:9 enhanced or anamorphic.   This means square pixels are converted to rectangle (anamorphic) pixels, so when played on a 16:9 widescreen television, the footage is stretched back out horizontally in the same proportion so that the widescreen image fills the screen at full resolution without shape distortion.