To say that HDTV is as big an advancement to television as color was back in 1953 is an understatement worthy of a Foster’s beer commercial. Let’s face it, Gilligan’s Island bridged the gap between black-and-white and color, and about the only thing that changed was the opening credits—and color had little to do with the Professor and Mary Ann being added to the roster. HDTV, on the other hand, adds much more to your TV-watching experience. Let’s consider its five most important benefits:
Widescreen
The most obvious difference between regular TV and HDTV is the latter’s wider image. HDTV’s aspect ratio, or ratio of image width to height, is 16 units wide for every 9 units high. This is expressed as 16:9 but can also be referred to as 1.78:1. (This is just simple math; 16 divided by 9 equals 1.78.) Regular TV images of the same height would be only 12 units wide (12:9 or 4:3, aka 1.33:1). This gives the high-definition viewer a much wider viewing landscape, one that matches more closely with human vision, which is accustomed to watching a wide field of view. The wide image is also closer to the aspect ratio used for most theatrical presentations. This means most movies played on HDTV will not have to be cropped or letterboxed much for the images to fit the screen as they would a regular TV. Shows recorded and broadcast in high definition, however, will fill the screen entirely.
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| WIDESCREEN ADVANTAGE: HDTV offers a widescreen image much like you see in a movie theater. The aspect ratio (i.e., ratio of width to height of an HDTV display) is 16:9 or 1.78:1. Regular television has an aspect ratio of 4:3 or 1.33:1. Movies, which can be filmed in aspect ratios as wide as 2.35:1, must be severely cropped or letterboxed (adding black bars above and below the image) to fit on a regular television. Most movies, which are shot in 1.85:1, will lose little if any image area or will have minimal black bars on an HDTV screen. Shows recorded specifically for HDTV will fill the entire screen. |  |
Clarity
In addition to the wider image, HDTV’s digital signals are much clearer than regular television’s analog signals. It’s like the difference between your old phonograph (did you even have one of those?) and a CD player. Think of two delivery trucks bringing the signals to your home. The analog signal is like something carried on an uncovered flatbed. Parts of the signal get lost in the wind, while unwanted dirt and grime might get mixed in with the surviving signal as it travels down the signal path to your TV. By contrast, the digital truck is enclosed, air-conditioned and airtight. So long as the truck reaches your house, whatever gets put into it is what’s delivered to your display. There’s no added grain, ghosts, distortion or loss in quality. Even if there isn’t a difference in resolution, signals recorded and transmitted digitally will be clearer and cleaner than their analog counterparts.
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| DETAIL AND COLOR THEORY: High- definition TV uses a greater quantity of much smaller pixels, or picture elements (simulated close-up at left), to create the image. The system also uses a wider color palette and has improved dynamic range. The result is a picture that’s substantially sharper with richer colors and a more three-dimensional appearance as compared to regular analog signals (simulated, at top). |
The country’s new digital television system allows broadcasters to alternate between a single HDTV signal and multiple standard resolution signals (visit the San Francisco PBS station’s website at www.kqed.org/ tv/digitaltv for a great example). Standard definition doesn’t necessarily offer any additional resolution over analog signals and therefore isn’t considered HDTV, but rather merely DTV. While this might still look better than analog signals, high definition, as the name implies, offers much higher resolution and looks substantially better. Most broadcasters use an interlaced HDTV format with a horizontal to vertical resolution of 1920 by 1080 picture elements, or pixels. This is commonly referred to as 1080i. Compare this with regular television, which has a vertical resolution of 480i and a horizontal resolution of 330 pixels or less per picture height, and you can see the difference without even seeing an image. Even DVD’s resolution, 720 by 480p, is no match for HDTV. The 1080i format has more than twice the vertical resolution and more than three times the horizontal resolution of regular television. Where before you could barely read the name on the back of a football player’s jersey, now you can practically count the individual blades of Astroturf.
There’s also a second, progressively scanned HDTV format called 720p (used by ABC, Fox and ESPN), which offers a 1280 by 720 resolution. Progressive images, without delving too deeply, have roughly twice the vertical resolution per sixtieth of a second of a comparable interlaced image. This gives the 720p format roughly three times the vertical resolution and over twice as much horizontal resolution as a normal TV signal. This resolution also matches with many digital display technologies, like plasma, DLP and LCoS. In fact, few displays as of yet can take advantage of 1080i’s full horizontal resolution.
Color and Dynamic Range
HDTV signals also have improved color and dynamic range. The color palette with high definition is much wider than with regular TV. Reds and greens can be much deeper and more saturated, which gives the image a much richer and more vibrant appearance. Dynamic range, or the difference between peak white and pitch black, is also slightly improved. This means that gradations from light to dark are smoother. These elements combine with the increased resolution to make HDTV look great.
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| SOUND SCIENCE: The diagram (top) illustrates that the 5.1 channels are totally discrete. This means that each channel is independent of the others, providing better separation and clarity. In a typical analog system (bottom), you can derive center, surround and subwoofer effects only from the existing two channels of audio. The audio is never truly separated and won’t sound nearly as enveloping or immersive. |
HDTV is more than just great images. The audio is equally as impressive as the video that accompanies it. The same Dolby Digital soundtrack heard on DVD and in the best movie theaters can now accompany all of your favorite TV shows. This includes left, center, right, left surround and right surround channels, as well as a low-frequency effects channel (the ".1"), for a totally enveloping audio experience. Dialogue stays anchored to the screen while other sound effects travel around the room. Ambient sounds from the two rear speakers immerse you in the middle of an action scene or sporting event, while the subwoofer fills in ultralow frequencies, making the sound rich and full-bodied. As it was with the introduction of stereo TV broadcasts, the full 5.1 soundtrack may not be used for all shows, or may not be passed along by your local station, but when it is and you have an audio system to accommodate it, you’ll hear the difference.
I can write about wider, clearer, more- detailed, colorful and dynamic images with enveloping soundtracks until I’m blue in the fingertips and it won’t do HDTV justice. You have to experience it for yourself. Would high-def have turned Gilligan into Seinfeld? Of course not—every episode would still culminate in the title character predictably foiling the group’s escape from the island. But we would definitely have enjoyed a more three-dimensional, lifelike quality in the flora, fauna and Ginger’s swimsuits. Now consider shows like Alias, ER, The West Wing and CSI: Crime Scene Investigation, to name just a few. In HDTV, these shows take on a near-cinematic quality, which means you no longer have to wait until the weekend DVD rental to enjoy a movie at home. The bottom line is, if you like TV, you’ll love HDTV.