Primed goes in-depth on the technobabble you hear on Engadget every day -- we dig deep into each topic's history and how it benefits our lives. You can follow the series here. Looking to suggest a piece of technology for us to break down? Drop us a line at primed *at* engadget *dawt* com.


Like so many things in life, when it comes to high-definition televisions, size matters. So, too, does picture quality -- we like watching the devil in crisp detail, after all. As the centerpiece of home entertainment systems, today's flat big-screen HDTVs pull triple duty. They're the preferred display when you're braining zombies during a flesh-tearing PS3 game of Dead Island. They're ideal for watching zombies (er, walkers) get brained on AMC's hit The Walking Dead. And in terms of social status, big HDTVs serve notice that, yes world, you've arrived. So join us as we explore and demystify the acronym-filled habitat of HDTVs -- and in the process maybe save your bank account from getting bitten.

In this installment of Primed, we'll examine the two main breeds of flat-panel HDTVs, including a look at liquid crystal display and plasma technologies. We'll also put screen size, resolution and frame rates under the microscope. We'll wrap things up with a view of what's on the high-def horizon and close out with a critical assessment of 3D HDTV. Strap yourselves in, couch jockeys, it's time for Primed.

Table of Contents
Rewind
Mind your p's & i's
Back in black
LCD
Fast-forward
Not ready for prime time
Wrap-up

Rewind
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Folklore tells us Philo Farnsworth was fourteen when, in 1921, he hit on the idea of an image dissector -- to wit, television. What an awesome invention. And what an awesome name! You go, Philo. As the story goes, the inventor of modern TV drew inspiration from the back-and-forth plowing and planting of potatoes on the family farm in Idaho.

US Patent and Trademark Office records show us that Farnsworth received a patent for history's first fully electronic television system in 1927. His image dissector converted individual elements of an image into electricity, which could be transmitted and "painted" onto a screen one line at a time. More specifically, his device was a tube that captured an image through a glass lens and focused the image onto a plate coated with cesium oxide (Cs20). When light struck the cesium oxide-coated plate, it emitted negatively charged photoelectrons. Electrostatic deflecting plates then arranged the electron image into rows of lines. In fact, Farnsworth's first successful TV transmission in 1927 was just one flat line, sort of the C-SPAN of its day.

Smash cut to November 1936, North London. The BBC began transmitting the world's first "high-definition" service on one channel to an audience of hundreds. These daily, two-hour broadcasts were only high-def when compared to previous mechanical transmission systems, which delivered as few as 30 lines of resolution. Those early BBC broadcasts displayed as many as 405 lines. And that's how it was before the digital era. Your grandma's RCA cathode ray tube analog TV displayed images in lines, not pixels. As we will see, modern high-definition raised the bar on resolution. In any case, the British commandeered all the equipment for national defense when the Nazis launched WWII and started bombing London. Talk about a buzz kill.

The French and even the Russians moved the needle on high-definition TV. France rolled out an analog system in 1949 that delivered 819 lines, which technically would be high-def by today's standards, but it broadcast only in black-and-white. About a decade later, the Soviet Union announced it developed something it called the Transformator, a high-def analog TV system capable of 1,125 lines of resolution. The Russians never deployed it, however.

NHK in 1979 unveiled the world's first consumer digital HDTV

Our HDTV globetrotting continues to Japan, where state broadcaster NHK in 1979 unveiled the world's first consumer digital HDTV, known as the Hi-Vision or MUSE system after its Multiple sub-Nyquist sampling encoding compression technology. It still was a bandwidth hog, requiring about twice the signal processing of the analog television system used in North America at the time. And the display aspect ratio -- the ratio of the width of the screen to its height -- was 5:3, not the eye-friendly 16:9 standard found in TVs today. Yet MUSE had four times the resolution of analog. The future came into focus. High-definition television was upon us.


Mind your p's & i's
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As in any era of technology transition, there was chaos in HDTV's formative years with countries and companies adhering to different systems. By 1996, some semblance of domestic order came when the Federal Communications Commission approved HDTV and digital TV broadcasting standards, which the Advanced Television Systems Committee embraced. As of June 2009, all so-called full-power analog TV broadcasts ended in the United States with the switch to digital transmitting, capable of supporting more channels and programming with greater audio and video fidelity. The rest of the world uses a slightly different set of rules, so we'll concentrate on the ATSC standards here.

As indicated, the powers that be nailed the aspect ratio at 16:9, wider than TV screens of yore but not as expansive as the Panavision / Cinemascope aspect ratio of 2.39:1 found in big movie theaters.

The standards get a little trickier when it comes to resolution, which is measured in pixels, the tiny dots that create digital images or, more accurately, the smallest element of an image that can be individually processed in a video display system. To be sure, the Imaging Science Foundation will tell you that resolution isn't the most important aspect of picture quality. The top three, in order, are contrast ratio, color saturation and color accuracy. Resolution is fourth on the list. But the ATSC at least defines the standard for high-def resolution. Manufacturers can use whatever scale they like to measure, say, the contrast ratio of their displays. Without a standard, specs for contrast ratios, color saturation and accuracy are more or less meaningless.

Generally, the more pixels you can cram on a surface, the sharper the image. The ATSC set the highest HDTV resolution at 1,920 x 1,080 -- that is 1,920 pixels on each of 1,080 horizontal lines for a total of 2,073,600 pixels per screen. Standard definition is about 704 x 480 for a total of 337,920 pixels per screen. So HDTVs can offer more than six times the resolution of analog TVs. They can. But not always.

You'll see flat-panel HDTVs marked with a resolution value followed by the letter "i" or "p." The ATSC set the floor for high-def resolution at 720p. Most of the high-end HDTVs on retail shelves will have a resolution value of 1080p. Some lingering models may have 1080i. The numbers indicate the set's native resolution -- the resolution at which the set is designed to display images and the absolute limit on the amount of detail it can produce.

The "i" stands for interlaced; the "p" stands for progressive scan. Interlaced displays draw every other picture line and then loop back and draw the remaining lines -- 1, 3, 5, 7 ... then lines 2, 4, 6, 8, and so on. And they do this in blazing fast frame rates. An HDTV with a frame rate of 120Hz (hertz) or 120 cycles per second will redraw every odd-numbered line 60 times a second and then redraw every even-numbered line 60 times a second. Video purists note that this alternating aspect of interlacing can cause a flickering effect. But most of us won't notice. That is, unless we're watching the same show on a progressive scan HDTV side-by-side with the interlaced HDTV. Progressive scan HDTVs draw all the horizontal lines in order. An HDTV at 120Hz can draw every horizontal line 120 times a second, making for a smoother motion picture.

In the world of HD broadcasting, 1080p at 60 frames per second is better than 1080i at 30, but it's also more elusive because it takes more bandwidth. Broadcasters would have to drop channels to transmit in 1080p, for something that would go unnoticed by most.

"For the most part," says Dave Pedigo, senior director of technology at the Custom Electronic Design & Installation Association, "satellite and cable providers are delivering 1080i or 720p." Regardless of what the specs say on your HDTV, notes Pedigo, if your provider is transmitting 720p, your resolution will be limited to 720p. Take the 80-inch giant Aquos LC-80LE632U from Sharp, which will run you about five grand. The thing is half as long as our 2000 Jeep Grand Cherokee -- coincidentally also worth about five grand. On Page 74 of the Aquos operation manual under the Troubleshooting section, it notes one of the reasons for poor picture quality of HD programs: "The cable / satellite broadcast may not support a signal resolution of 1080p."

Likewise for your peripherals. If your DVD player is 720p, your 1080p HDTV will convert it to 1080p, which will be a far cry from 1080p content. No matter the resolution of the source material -- DVD, game console, broadcast, etc. -- a fixed-pixel display will always convert or scale it to fit its native resolution. In a perfect world, the source resolution would match to your TV's native resolution to avoid any picture anomalies that can occur from up or down scaling. But even low-end high-def is amazingly crisp, so most probably won't notice the difference.

For every frame of an image, the HDTV inserts an approximation of the next logical image based on the preceding image. The fabrication is called an interpolated image.

That said, Pedigo recommends 1080p HDTVs. Most Blu-ray discs are formatted in 1080p. And if you want to watch HD broadcasts in 3D, you'll need 1080p, among other things. More on that in a few. Almost as elusive as 1080p broadcasts are those upper-end frame rates. Again, take the 80-inch Aquos from Sharp. It boasts a robust 120Hz frame rate. But most cable and satellite providers send images 30 frames per second. Your 120Hz HDTV will have to repeat frames to achieve the 120Hz speed. And that may not add much in the way of picture quality, as it's only adding an image that wasn't there to begin with.

When it's receiving a signal at 60Hz, a 120Hz HDTV is refreshing pixels through a process known as motion estimation, motion compensation or MEMC. For every frame of an image, the HDTV inserts an approximation of the next logical image based on the preceding image. The fabrication is called an interpolated image.

For HDTVs with 240Hz refresh rates, three interpolated images are inserted between each true frame. Awesome, you might think, especially if you're watching fast-moving broadcasts such as sports. Mind you, you won't be able to distinguish these interpolated images from the real ones. They're whizzing by too fast. But you'll "feel" the speed. Which is why Yung Trang, president of Techbargains, offers this word of caution. "If you watch a movie in 240Hz, it can look like it was filmed on a camcorder," he says. "And some folks get motion sickness. I've gotten motion sickness." Fortunately, this is a feature that you can toggle on or off.


Back in black
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Big, flat-screen HDTVs come in two primary species: plasma and liquid crystal display. Sure, you can still buy rear or digital light projection HDTVs. They cost far less than plasmas and LCDs. But they're bulky -- they require space for a projector in the back, after all. So they don't fit the modern concept of sleek. It'd be like having your buddies over to listen to your collection of Yes on that Pioneer CT-F2121 stereo cassette tape deck -- a little dated. Moreover, rear-light projection HDTVs have poor picture qualities in comparison to plasmas and they're awful to watch in bright rooms.

Plasmas and LCDs are price competitive. You can pick up a 65-inch internet- and 3D-ready, 1080p LCD or plasma HDTV for about $2,500. But overall plasma HDTVs tend to perform a little better -- unless you're living in high-altitudes.

Plasma display panels contain an array of hundreds of thousands of small, luminous cells sandwiched between two panes of glass. The cells hold neon, xenon and other inert gases and just a touch of mercury. Don't freak out. Fluorescent lights have mercury. Indeed, the cells in plasma TVs are like neon lamps -- they glow when electrified through electrodes.

When charged, mercury is vaporized and gas in the cells form a plasma. Electrons strike mercury particles in the plasma. This momentarily increases the energy level of the mercury molecule, which sheds the energy as ultraviolet (UV) photons. Lower energy photons are mostly in the infrared range. But about 40 percent are in the visible light range, so the input energy is shed, mostly as heat or infrared, but also as visible light. Depending on the phosphors used, different colors of visible light are emitted. Varying the voltage to the cells allows different colors.

When charged, mercury is vaporized and gas in the cells form a plasma.

Plasma displays use the same phosphors as the old cathode ray tube TVs, which accounts for plasma's extremely accurate color reproduction -- better blacks, better whites and better contrasts than LCD displays. But plasma's use of gas also factors into its challenges at altitudes generally 6,500 feet above sea level. Manufacturers compress gases inside plasma cells calibrated at or around sea level. Thinner air at higher elevations causes pressure imbalances in the cells. Plasma TVs have to work harder to compensate. This has been known to trigger an audible buzz from the cooling systems used to regulate temperatures of plasma displays.

You also may hear that plasma HDTVs have a tendency to "burn" images onto the screen. That was true years ago, not today. Screen burn-in occurs when an image is left too long on a screen. Newer plasmas are far less susceptible to this. Yes, it can still be a problem. But after a few days most burnt-in images fade.


LCD
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Liquid crystal displays use light modulating properties of liquid crystals, which don't emit light directly. LCD televisions produce a black and colored image by selectively filtering a white light. The light source comes from a series of cold cathode fluorescent lamps (CCFLs) at the back of the screen. Some LCD TVs have a row of lamps on an edge; others that offer better contrast have rows of backlights across the back of the screen. (See our Primed on LCD fundamentals for more information about that breed of display.)

LCD HDTVs are lighter -- they use plastic screens; plasmas use glass. Weight is a factor if you're considering wall-mounting. LCD HDTVs also are more energy efficient than their plasma counterparts. LCD power-use trends from 2003 to 2010 show a sharp reduction in active and standby modes, according to the Consumer Electronics Association. Active mode power density dropped from 0.35 W/in² in 2003 to 0.13 W/in² in 2010, a 63 percent decrease; for standby mode, power consumption swooned from a high of 6.1 m W/in² in 2004 to 0.77 m W/in² in 2010, an 87 percent decline. Plasma TV power-use rates also saw similar declines. However, some plasmas still use two to three times as much power as some LCD TVs.

But because of the backlighting, LCD displays can't -- yet -- achieve the rich black and deep contrasts of plasmas. For LCDs, at least for today, there's always going to be some light leakage from between pixels. As LCD technologies such as polarizing filters and dynamic backlights improve, the image-quality gap between LCDs and plasmas is narrowing.


Fast-forward
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Internet-ready HDTVs sound like the next logical technological evolution. Indeed, manufacturers have a slew of net-connected televisions on the market, as well as a wide array of apps and add-ons. So-called smart TVs come with video-streaming services such as Hulu Plus, Netflix and YouTube; video-on-demand, including Vudu and CinemaNow; web radio services; and all kinds of special apps for sports, entertainment, photos and even full web browsers. Samsung has a remote control with a QWERTY keyboard on the back to help navigate the UI. Logitech and others sell web TV keyboards. But with so many different apps and no single, simple user interface, the smart TV space is a bit chaotic at the moment. If you want to access internet content through your HDTV, you might want to consider a Blu-ray player, game console or a set-top box.

OLED (Organic Light Emitting Diode) HDTVs are another potential promising tech-step forward. OLED TVs are brighter, more energy efficient, thinner and offer better refresh rates and color contrasts than LCDs or plasma. But their screen size currently is limited -- LG unveiled a 31-inch prototype earlier in 2011 and has indicated it will have a 55-inch OLED HDTV out in 2012. Like all new high-end, high-tech, first-generation models, these will be very expensive. LG's 15-inch OLED TV, available in Korea and Europe, costs about $2,500.

Meantime, you'd think with frame rates so fast you need to watch Adam Sandler movies with a barf bag -- advisable under any circumstance, really -- screen sizes as big as Smart Cars and resolutions so fine you can count nose hairs that HDTVs are reaching a performance plateau. Think again.

Yes, human vision has its physical limits. The sun's temperature determines the colors or wavelengths emitted, while gravitational strength determines the composition of Earth's atmosphere, which determines the amount of wavelengths let through. Of the 70 octaves of radiation in the universe, human eyesight is able to detect only one in the 360 nanometer to 720 nanometer range.

But that's not stopping HDTV advancements. Yung Trang of Techbargains notes that even today's TVs enhance and sharpen images. "They make the greens of golfing broadcasts slightly greener," he says. "The picture enhancements are shockingly sharp -- better than real life."

He and others say we have not reached the peak. While the sweet-spot of HDTV screens is in the 40-inch to 60-something-inch sweet spot, higher resolutions will allow HDTVs to grow even larger while delivering super-sharp images.

So-called Quad HDTV promises to have a resolution of 2160p capable of displaying 2160 horizontal lines using progressive scanning and 3340 vertical lines for a total pixel count of 8,294,400, or four times the total pixel count of 1080p -- hence the "quad." Trang predicts these sets will hit the market in two to five years and retail for upwards of $10,000 at first. Dave Pedigo of the Custom Electronic Design & Installation Association envisions another scenario -- quad def will allow you to watch 3D HDTV without the glasses.


Not ready for prime time
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The hype machinery has been working overtime for 3D HDTV. Box office 3D hits such as Avatar, combined with advances in home electronics technology, have put 3D HDTVs within reasonable price reach and into living rooms. Panasonic bet heavily on 3DTV, but soft demand will contribute to an annual net loss of $5.5 billion dollars. Meanwhile, Sony, another big booster of 3DTV, in early November said it is going to restructure its TV divisions in hopes of turning around its struggling TV business. Before we discuss why the 3D hype is misaligned with current reality, let's take a look at what 3D is.

We perceive depth when our brain takes images from our left and right eyes and merges the images into one. When we watch video on a flat screen, the right and left eyes see the image shot from a single camera, allowing us only to perceive the image in two dimensions -- horizontal and vertical, but no depth. 3D TV requires an image to be shot and displayed from two slightly different angles. All 3D technologies use this principal of stereoscopic vision, where each eye sees a slightly different image, which the brain interprets as the perception of depth.

3D TV requires an image to be shot and displayed from two slightly different angles.

Most all 3D HDTVs require you to wear a pair of special glasses to achieve the 3D effect. The two main types of 3D glasses are active and passive. Older anaglyph passive glasses have two different color lenses (red and blue) to filter the images on the television display screen. Many of us recall the primitive cardboard kind that, well, never really worked. In the passive glasses world, the 3D TV displays two images at the same time, one with reddish tint and other bluish slightly offset from each other. With anaglyph glasses, the blue lens absorbs all the blue light allowing you to see the reds and -- you know where this is headed -- the red lens only allows you to see the blue-tinted images. Each eye only sees one image. But the passive glasses essentially trick the brain into interpreting that there is one image. By combining the two images into one, the brain produces the 3D effect. Modern passive glasses use polarized lenses, but the concept is still the same. Instead of using two sets of images with different colors, the polarization technique alters the waves of light the viewer sees.

Active glasses require a power source, typically a small battery. Active glasses alternately open and close the view of each lens to show each eye a different image at any time. This means that the 3D glasses need to be synchronized with the 3D television display, done through infra-red technology between the headset and TV. Unlike passive glasses, active 3D glasses don't alter the display of colors, so they offer far better picture quality.

The forthcoming super high-end 3D HDTVs will do away with the need for glasses. These TVs use filters or lenses -- a parallax barrier -- atop the display screens to direct separate images to the left and right eyes. You need to sit in front of the TV and at a certain distance to get this 3D effect, which isn't fun if you're the one having to sit off to the side. To be fair, all televisions are best view from the front.

So to recap, 3D technology isn't quite there. Wearing glasses -- even sleek active glasses -- is a drag, especially for long movies. And the glasses-free 3D HDTV remains a work in progress. But that's not the only thing putting 3D HDTV in a holding pattern. Dearth of content is a major factor, according to a Retrevo Pulse report conducted in October. The report is part of Retrevo's ongoing study of people and electronics. While high prices used to be the consumer turn-off, some 40 percent say there's not enough programming to watch. "Content will continue to be an issue until there are enough blockbuster shows in 3D like the Super Bowl, the Academy Awards, and more movies like Avatar to make everyone want to go out and buy a 3DTV set," the report states.

What may be even more disconcerting for manufacturers: "More than half (55 percent) of HDTV buyers say they're not interested in 3D even if the price difference is small."

The report adds that the "wildcard" in the 3D HDTV market will be video games. Pedigo concurs. "As more games come out in 3D, especially the first-person shooting games, you could see an uptick in 3D," he says, adding that 3D technology is relatively inexpensive to plumb into TVs. "It will become standard," he says. "Not an option."


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You can buy a 47-inch HDTV for less than $650, a price drop of about 20 percent from the previous year, note analysts. You'll pay more for the bigger screen, internet-ready models with higher-end specs. But at least you'll be well-armed with information not to be snowed by fast-talking sales reps. You'll want that HDTV with 1080p, but you'll know that cable and satellite feeds won't deliver all the resolution richness that the technology allows. You'll want 1080p native resolution because your Blu-ray discs and games use that setting. Another parting bit of buying wisdom: you'll almost never see a live broadcast in a retail setting, largely due to copyright issues. The feed will be from a disc or hard drive. Now you can shop for that high-definition television with eyes wide open and with clear vision.


[Image Credits: Farnsworth Archives, ATSC, DTV Express, KTH, K.I.D., HK Physics World and Tattoo Temple]

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