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September 2002|As a producer of digital content, the transition to Digital Television (DTV) will force you to make a difficult decision. If you release video in full-frame format, your content may have a limited lifespan. By contrast, producing widescreen content is future-proof, but may aggravate existing customers. In this article, we will examine the evolution of full-screen and widescreen formats, reveal how they are adapted for the TV-based delivery market and provide recommendations of which aspect ratio you should use for your content. A Simpler World The reason for so much uncertainty surrounding aspect ratios (the relationship between picture width and height) is the FCC's mandate that television become completely digital by 2006. Besides improved clarity, the FCC mandate will enable High-Definition Television (HDTV) resolutions and aspect ratios. Unlike traditional analog television images, which are exclusively interlaced, HDTV content may be presented in progressive or interlaced format. Progressive images are drawn instantaneously, while interlaced pictures are shown in two passes (i.e., the odd lines are drawn first and the even lines are displayed in a second pass). Although an interlaced image isn't as crisp as a progressive one, HDTV's increased resolution and digital transmission capabilities guarantee that either format will dramatically improve today's analog broadcasts. To obtain this stunning picture quality, both HDTV formats leverage wide aspect ratios. The progressive flavor of HDTV is known as 720p (the "p" stands for progressive), and it offers a resolution of 1280x720 (a wide aspect ratio of 1.78). Similarly, there is one interlaced HDTV format called 1080i (the "i" represents interlaced), and it supports a resolution of 1920x1080 (a wide aspect ratio of 1.78). Since most users don't have widescreen televisions, they will either need to buy a new TV or an adapter for their current TV to display 720p or 1080i content. The prospect of new resolutions and aspect ratios has invigorated a television infrastructure that has been stagnant for decades. Before the early 1950s, all content was produced in a single aspect ratio: 1.33 horizontal pixels for every vertical pixel (or 1.33:1). Once the 1.33:1 aspect ratio was adopted by the Academy of Motion Picture Arts and Sciences in the early 1930s, it became a de facto stan- dard for movies and was nicknamed the Academy Standard. Technically, the ratio they adopted was actually 1.37:1 (it was slightly modified to accommodate sound), but for the purposes of this article, 1.37:1 and 1.33:1 are functionally and visibly equivalent. Alas, this nirvana was permanently altered with the acceptance of the television. Since viewers were already accustomed to the 1.33:1 aspect ratio, the National Television Standards Committee (NTSC) decided to reuse this aspect ratio for TV broadcasts (the aspect ratio for TVs is also referred to as 4:3 since there are four horizontal pixels for every three vertical pixels—the same ratio as 1.33:1). While a common aspect ratio fostered the explosive growth of TVs, it also triggered a startling decline in theater attendance. Since both mediums had the same aspect ratios and produced the same viewing experience, there was no compelling reason for people to watch pictures in a theater. Fortunately for the studios, this trend was reversed by the introduction of content with wider aspect ratios. Wider aspect ratios were effective in attracting and keeping viewers because they more closely approximated the viewer's range of vision. Human eyes have a rectangular, and not square, vision range (i.e., you see more horizontally than vertically). Therefore, the wider the image, the more likely you are to pay attention. In addition, wider images enable the content producer to cram additional details into each video frame further captivating the viewer. Although Hollywood experimented with numerous wide display techniques, two eventually predominated: flat and anamorphic. Flat aspect ratios are obtained by reducing the vertical aperture (visual area) of the projected image. In effect, the top and bottom of the image are chopped off. The resultant wide image is projected onto a large screen. Most flat movies are shown in the Academy Flat (i.e. 1.85:1) aspect ratio (hence, this aspect ratio is also nicknamed Flat). Movies in this category include The English Patient, The Birds, and North by Northwest. While this approach does yield wide images, it has limitations. First, since wide images are obtained by sacrificing vertical resolution, so much content must be cropped to achieve an extra wide aspect ratio (such as 2.35:1), that it is impractical. Furthermore, since flat projectors rely so heavily on vertical resolution reduction and magnification of the cropped image, dirt, graininess, and other artifacts on the film become more noticeable. Fortunately, advances in film technology have minimized the likelihood of such artifacts affecting today's movies. To overcome the limitations of flat projections and to obtain extra wide aspect ratios, content producers often rely on anamorphic or "controlled distortion" lenses. This controlled distortion process squeezes a wide image onto film. To display these images, a projector with an anamorphic lens reverses the process and restores the film to its original wide aspect ratio. The dominant anamorphic aspect ratio is 2.35:1 (aka Anamorphic Scope or Scope). Since anamorphic content is so dependent on the lens technology, it is often re-ferred to as Panavision or Cinemascope. Cinemascope describes a projector lens that may be used to project anamorphic images and was championed by 20th Century Fox, while Panavision is a corporation whose lenses dominate the wide-screen arena. Popular anamorphic movies include Episodes 4-6 of the Star Wars saga and Blade Runner.
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