Aspect Ratio of the Video Frame

The ratio of horizontal to vertical dimensions of a film or video frame is called the aspect ratio. Aspect ratio is independent of absolute image size or resolution.

Figure. Diagram showing the aspect ratios for standard definition video, high definition video, standard cinema, and widescreen cinema.

Aspect ratios can be expressed as absolute dimensions (4 x 3), a ratio (4:3), a fraction (4/3), or as the decimal equivalent of a ratio (1.33:1, or simply 1.33). Aspect ratios are generally expressed according to the following conventions:

Below is a list of commonly used aspect ratios, mostly from the film and television industry, plus a few others for comparison.

Aspect ratio
Medium
1.33 (4:3)
Early 35 mm film and SD television
1.37
4-perforation 35 mm camera footage (prior to projection)—also known as “Academy” aspect ratio
1.66 (15:9)
Standard European film; masked in projector
1.78 (16:9)
HD television
1.85
Standard North American and UK film; masked in projector
2.40 (also referred to as 2.35 and 2.39)
Widescreen (anamorphic) film projection

Footage with different aspect ratios can be combined using a variety of techniques, as described in the following sections.

Letterboxing

Letterboxing preserves the aspect ratio of widescreen movies on a narrower screen. The movie is scaled until it fits within the width of the screen, resulting in blacks bars at the top and bottom of the frame.

Figure. Diagram showing examples of letterboxing.

Pan and Scan

The pan and scan technique crops widescreen movies to fit on a narrower screen. In some cases, artificial camera moves may even be added to show the entire content of a widescreen frame. Pan and scan does not preserve the aspect ratio of widescreen movies.

Figure. Diagram showing the pan and scan method of cropping widescreen movies.

Anamorphic

Anamorphic techniques use special lenses or electronics to squeeze a widescreen image to fit in a narrower aspect ratio. During projection or playback, the squeezed image is stretched back to its original widescreen aspect ratio.

Figure. Diagram showing examples of anamorphic changes to widescreen images.

Anamorphic video can also be letterboxed. For example, 16:9 anamorphic DVDs may contain letterboxed 2.40 aspect ratio footage.

Pillarboxing

Pillarboxing displays movies with a small aspect ratio on a wide screen. Black bars appear on the left and right sides of the frame.

Figure. Diagram showing an example of pillarboxing with black bars appearing on the left and right sides of the frame.