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
'Save me Panasonic, you're my only hope.'
(Credit: Panasonic)With Pioneer and Vizio recently announcing their exits from the plasma market, there's been a lot of chatter about the technology's short and long-term viability. Some of plasma's problems are PR related. Lingering questions--justified or not--about burn-in and energy efficiency have become part of the public conscious and remain a stumbling block at point of sale. Ultimately, however, there are more simple economics at play. Far more factories are available to produce LCD displays than plasmas, which haven't been able to maintain their price advantage as margins have eroded and the performance gap between the technologies has narrowed.
But let's not dwell on how we got here. The key question is how can plasma survive? And for better or worse, the answer is really in the hands of Panasonic, the brand that has most closely linked its TV fortunes to the technology. Yes, Samsung and LG make lots of plasmas--and some good ones, too--but both are also well-committed LCD and well hedged should plasma go away (Panasonic makes some LCD TVs as well, but nothing larger than 37 inches, while plasma starts at 42). Alas, with Pioneer's departure--a sad day for those who value great TV picture quality--Panasonic is left to carry the plasma mantle largely on its own.
Can it keep plasma from perishing? Well, I hope it can, because the TV space is already commoditized enough and it would be shame if we went down to one flat-panel technology (sure, OLED is being hyped as the display technology of the future, but it's years away from mass-market adoption). However, Panasonic's got to take make some key moves to keep plasma from running out of gas. Here they are:
... Read MoreAround the holiday season we get a lot of e-mails from readers agonizing over what TV to buy. With the economy the way it is, consumers aren't completely shying away from buying new TVs, but they're on tight budgets and appear to be predominantly interested screen sizes 52 inches or smaller. The big problem with going bigger is that you jump into a whole new price class when you start looking at the Panasonic 58-inch plasma--and it gets worse when you check out Pioneer's 60-incher. The exception to all this is DLP-based rear-projection HDTVs, where Samsung and Mitsubishi are the only real remaining players. Remarkably, Best Buy is selling our editors' choice Samsung HL61A750 for $1,600 and the 67-inch inch model in the same line goes for $2,000. Meanwhile, Best Buy has the 65-inch Mitsubishi WD-65735 for a mere $1,500.
Baby got back: On the surface, Samsung's 61-inch 1080p LED-Powered DLP HDTV looks like a plasma or LCD--but it's not.
(Credit: Samsung)But rear-projection is a dying breed, right? Or, as one reader commented, "Everyone seems to be getting out of the rear-projection market. What happens if Samsung completely kills it? What happens then? Will they service my TV?"
Yes, most pundits agree that rear-pro is indeed on its way out. I've said as much in earlier columns. And in his review of the Samsung HL61A750, senior editor David Katzmaier wrote, "The way things are going, 2008 or 2009 may be the last year for rear-projection, lasers notwithstanding." As for lasers, he was referring to Mitsubishi's Laser TV, which, at $7,000 is a whole other beast we won't get into (Mitsubishi hasn't sent as a unit for review, but we hope we get our hands on one at some point). But with Sony, Panasonic, Hitachi, and others exiting the rear-pro market, things look pretty bleak. We used to have three technologies to choose from in this category (LCD, LCoS, DLP) and now we're down to DLP (the aforementioned Laser TV is actually a laser-powered DLP set).
Ironically, the bad economy may save rear-projection. That Samsung HL61A750 is one of the most popular products on CNET and it would appear that many people are willing to give up the whole thin factor of plasma and LCD for more screen size at a lower price point. The Samsung solves a couple of problems inherent to rear-pro DLP: it uses LEDs instead of a conventional bulb, which eliminates the rainbow effect (some people can see brief streaks of color with bulb-based DLP). The LEDs also last much, much longer than bulbs--they give you about 20,000 hours of life.
Rear-projection still has its disadvantages, aside from the obvious fact that it's not flat and so usually can't be hung on a wall. RPTVs lose brightness and picture fidelity when seen from off-angle--to either side or especially above and below. Than again, so do flat-panel LCDs. RPTVs can also be subject to geometry errors, where some lines that should appear straight, such as the bars to either or above and below the screen, are instead subtly curved. The middle of the screen on DLPs is usually brighter than the edges, and other uniformity problems can be seen on some models.
In reality however, most of these picture quality issues are subtle and well worth the savings to big-screen shoppers. So, the big question simply is, if the manufacturers jettison the remaining rear-pro TVs, will they keep servicing them should they break down?
I'm not in the business of making guarantees, but if you look at Sony, they've continued to support and provide parts for their LCoS-based SXRD TVs in the field (there are plenty of them), so I think that's a pretty good indication that Samsung and Mitsubishi will do the same. All I know is that I'll soon be in the market for a new large-screen TV and unless 58-inch and 61-inch plasmas get a whole lot more affordable over the next 6 months, I'm strongly considering rear-pro. It's hard not to at these prices.
Anybody agree or disagree? Please comment.
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