Aspect Ratio

An Aspect Ratio is a measure of the ratio between the width of an object its height. When talking about video there are 3 different types of aspect ratio, the display aspect ratio, the pixel aspect ratio and the frame aspect ratio.

An aspect ratio is typically given as a ratio of width to height, for example a 4:3 aspect ratio means that the every 4 units of width there are 3 units of height, i.e. the object is 1.33 (4/3) times wider than it is high.

Display Aspect Ratio (DAR)

The display aspect ratio is the most commonly used term and will often be refered to as just the aspect ratio.

This term refers to the ratio of the video as displayed in it's final form. The two most common display aspect ratios are 4:3 (Standard Video) and 16:9 (Widescreen).

The display aspect ratio desccribes the size on the screen of the final video. This ratio is actually a combination of two other ratios. It is dependant on how many pixels there are in the width and height of a video (Frame Aspect Ratio), and the size with which each pixel is displayed (Pixel Aspect Ratio).

Frame Aspect Ratio

The frame aspect ratio describes the ratio between the width in pixels and height in pixels of each frame within the video. The frame aspect ratio is easily computed from the pixel resolution of a video.

For HD video the two common pixel resolutions are 1440x1080 and 1920x1080. 1440x1080 equates to a 4:3 frame aspect ratio and 1920x1080 equates to a frame aspect ratio of 16:9.

Pixel Aspect Ratio (PAR)

The pixel aspect ratio describes the ratio between the width and height of a single pixel when displayed.

The most common pixel aspect ratios are 1:1 (square) and 4:3.

Examples

Video ResolutionFARPARDAR
1440x10804:34:316:9
1920x108016:91:116:9