I've written articles in the past explaining various TV technologies, including the differences between 720p and 1080p and 120Hz and 240Hz LCD TVs. But with Samsung, LG, Sony, and other manufacturers pushing so-called LED TVs these days, it's high time that I--with an assist from our resident video guru, David Katzmaier--sort through all the marketing mumbo jumbo and provide some insight into just what an LED TV is. Here goes.
1. An LED TV is not a new kind of TV.
I appreciate a good marketing ploy as much as the next guy, but an LED TV is just an LCD TV that's backlit with light-emitting diodes (LEDs) instead of standard cold-cathode fluorescent lights (or CCFLs). And while they've become best-known this year with Samsung's ultrathin models, LED-backlit LCDs have been on mainstream store shelves since 2007, when Samsung's LN-T4681F debuted.
Unlike plasma and OLED, which are emissive technologies where each pixel is its own discrete light source, LCD is a transmissive technology where each pixel has to be illuminated from behind, or backlit.
2.There are two types of LED backlighting.
Initially, LED-based displays like the Samung LN-T4681F were backlit by what's referred to as a "full array" of LEDs behind the LCD across the back of the panel. But to create superthin TVs, engineers needed to eliminate that extra layer of LEDs and move it to the sides of the display. With this form of backlighting, the LEDs are affixed to all four sides of the TV and light is projected inward to the middle of the TV via "lightguides." These types of TVs are commonly referred to as "edge-lit" LED-based LCDs.
Samsung is the main maker of such sets this year with three series of edge-lit sets, although Sony did release one model earlier this year, the KDL-40ZX1M, and has another flagship series, the KDL-XBR10 models, waiting in the wings. Samsung, Sony, Sharp Toshiba, LG, and Vizio all have non-edge-lit, or "full array" models, available today. See our comparison of edge-lit vs. local dimming for more info.
3. Of the two, local dimming can produce deeper black levels, but also creates "blooming."
Local dimming LED backlights can dim or turn off individually as needed.
The type of backlighting can impact how deep a shade of black a TV can produce. All current LED-based LCDs with rear-placed, "full-array" LED backlighting--except the Sharp LC-LE700UN series--feature a technology called "local dimming." With local dimming, specific areas of the backlight can be dimmed or brightened when different areas of the picture get darker or brighter.
With fluorescent backlighting and edge-lit LED backlighting, by contrast, the entire backlight dims or brightens at once, if at all.
Being able to dim specific quadrants helps reduce the amount of light that leaks through to darkened pixels, and the end result is blacks that appear darker and more realistic. Since black levels are crucial to contrast ratio, the deeper the blacks, the more the picture--and colors--appear to pop. Also, the image as a whole will seem crisper. A great example of local dimming done right is Samsung's UNB8500 series, which is one of the best-performing TVs we've ever tested.
One downside to local dimming is an effect called "blooming," where brighter areas bleed into darker ones and lighten adjacent black levels. ... Read more
Samsung's sleek UNB6000 cuts a dashing figure, but it costs.
(Credit: Sarah Tew)We've already checked out one Samsung LED-based LCD TV this year, the UNB7000 series, but that's not gonna stop us from reviewing the less expensive version, logically called the UNB6000 series. The verdict? Still expensive, stylish and solid performing, minus a few issues like a fluctuating backlight and less than stellar uniformity.
In fact, aside from Yahoo Widgets, available on the 7000 but not on the 6000, the two edge-lit LED-based LCD displays (whew!) are basically the same. The 7000 uses a skosh more power and gets the tiniest bit blacker, while the 6000 gives ever-so-slightly better shadow detail and slightly a less-blue tinge in dark areas. But we're really splitting hairs: If you must have the thinnest TV on the block and want widgets, get the 7000. If you're still willing to pay more for thin but don't want widgets, go for the 6000. Simple.
On Sale Now: $1,199.00 - $1,499.00
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The high-end Samsung UNB7000 series is a looker.
(Credit: CNET)As HDTVs become more common--some would say commoditized--TV makers go to ever-greater lengths to justify higher price tags. Nobody is going as far as Samsung this year. The company is the only one thus far to announce a full lineup of edge-lit LED-based LCDs which cost a mint yet offer the most advanced technology and design you can get--at least until OLED comes along.
Each model among the three series of Samsung's "Luxia" lineup measures just 1.2 inches thick, thanks to that LED lighting system, which is also responsible for the TVs' excellent energy efficiency. The UNB7000 series is the middle child in price and features of the three; yet, it includes buckets of add-ons, many of them interactive, along with extensive picture adjustments including a cool new tweak-able dejudder mode. In our performance testing, we encountered some picture quality trade-offs caused by the LED system, namely less-than-perfect uniformity and off-angle viewing, along with the backlights' somewhat distracting fluctuations. These issues keep the UNB7000 series from earning our highest accolades for performance, but in terms of design and features the expensive Luxias set a standard that will be tough to beat.
Read the full review of the Samsung UNB7000 series.
Samsung's edge-lit LED-based LCD costs about $700 more than its non-LED counterpart. But it's really thin.
(Credit: Samsung)Samsung announced its new lineup of "LED TVs" at CES in January, and gave CNET editors a walk-through today to preview the technology. The company also set prices, and as expected, it'll cost you a fortune to take one of these thin models home.
The name "LED TV" sounds simple enough, but it's important to remember that these inch-thin sets are actually otherwise normal LCD (liquid-crystal display) TVs that use LEDs (light-emitting diodes) instead of the standard fluorescent backlights. But it gets even more confusing. We've reviewed LED-based LCD displays before, most recently the Sony KDL-55XBR8 and Samsung LN46A950--the two best-performing LCD TVs we've ever tested. A lot of the credit for those TVs' excellent picture quality can be attributed to their local dimming technology; groups of LEDs behind the screen can be dimmed or turned off to achieve those deep, inky blacks we all love so much.
The 2009 Samsung LED TVs we're previewing here do not utilize local dimming, so we don't expect them to match the picture quality of the local dimming sets. Of course, we'll know more once we can review one. In the meantime, we'll refer to the new displays as "edge-lit LED-based LCDs." More complex, we know, but also quite a bit more accurate.
The slideshow above goes into the nitty-gritty behind, or along the edge of, the technology. The short story is that the LEDs themselves are arranged along all four edges of the screen, and a special "light guide" sends light toward the middle. The result, according to the company, is similar uniformity characteristics to standard backlit LCD displays.
Edge-lit LED-based displays are also 40 percent more energy-efficient than standard Energy Star-certified LCD sets, and measure just 1.2 inches thick.
1.2 inches thin looks great from the side.
(Credit: Samsung)The downside is that they're extremely expensive. The cheapest model, the 32-inch UN32A6000 ($1,599), will cost more than twice as much as the company's standard 1080p 32-incher, model LN32B530 ($749) does. ... Read more
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The edge-lit Sony KLV-40ZX1M measures just 1.1 inch thick.
(Credit: CNET)As if 240Hz, 1080p/24 compatibility and contrast ratios in the millions aren't confusing enough, get ready for more product differentiation in the LCD TV space: two different kinds of LED lighting schemes. On one hand are relatively tried-and-true "local dimming" LED-based LCDs, which generally give great picture. In the other are "edge-lit" LED-based LCDs, which if the new Sony KLV-40ZX1M ($3,999) is any indication, do not.
We're sure the distinction won't stop marketers from trying to equate the two, however, and simply call them all "LED TVs," expecting consumers to assume that all LED-based LCDs give great picture. In fact, one company, Samsung, has already said it wants to create a separate "LED TV" category to differentiate the more-expensive, higher-tech-sounding sets from their lowly fluorescent-backlit cousins.
Also, who knows, maybe Samsung's upcoming edge-lit models, namely the 6000, 7000, and 8000 series HDTVs announced at CES, will perform better than the Sony KLV-40ZX1M we just reviewed. Lighter black levels and imperfect uniformity hampered its picture--as you might expect, the edges of the picture were brighter than the middle (go figure!). It sure looks cool though.
Read the full review of the Sony KLV-40ZX1M.
... Read more
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