2.5 Aspect Ratios
Just as depth of field and focal length define the image you're captur-ing, the aspect ratio defines the image's display. An aspect ratio simply describes the shape of the viewing screen by defining the relationship between a frame's width and height. The typical aspect ratio for television and video is 4:3, which is also called 1.33:1 in cinematic circles (see Figure 2.12). The first number (4) refers to the screen's width, and the second (3), its height. Film in theaters is shown at 16:9 aspect ratio, also described as 1.78:1 (see Figure 2.13). Now, high-definition television sets (HDTV) are bringing the 16:9 ratio into our homes (see Figure 2.14).
Figure 2.12 Most television is shown in a 4:3 aspect ratio, while films in theaters are shown at 16:9. Although still rectangular, a 4:3 ratio is closer to a square screen shape than a 16:9 ratio.
Figure 2.13 The 16:9 ratio, sometimes referred to as "letterboxed," is used most often for film.
Figure 2.14 1.78:1, or 16:9, is the aspect ratio of new HDTV and wide-screen televisions, as well as many films.
Most films released are kept to a safe 16:9 area, but their actual aspect ratios are 1.85:1 or higher.
How did these aspect ratios become the standard? When the first moving images were put on film, 4:3 was used, and it became the Academy Standard Aspect Ratio (see Figure 2.15). This aspect ratio remained until the 1950s, when wide-screen (16:9) aspect ratios emerged. In the '50s, television became immensely popular, and filmmakers needed a way to get people back to the movie theaters. By using an aspect ratio that was twice as wide as it was tall (2.35:1), they created a new cinematic experience. When an image extends to fill more of your peripheral vision, what you're watching is more engaging.
Figure 2.15 The 1.33:1 or 4:3 ratio was common in the early days of film.
Today, cinematographers use aspect ratios of 1.33:1, 1.37:1, 1.66:1, 1.78:1, 1.85:1, and 2.35:1. Each ratio is increasingly wider, and which you use is often determined by film stock, such as a large 70mm, or the type of production. The cinematographer must decide which aspect ratio works best for the budget and the overall look of the film. As a digital cinematographer, you have the freedom to experiment and mimic any of these real-world aspect ratios in your animation work.