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
Hz so good: The marketing of 240Hz TVs may rely heavily on test patterns.
(Credit: Akihabara News)Every year it seems there's a new catchy spec in the HDTV realm everybody likes to talk about. A few years back it was 1080p resolution. Then we heard about 120Hz, which is supposed to reduce motion blur in fast-moving images on LCD TVs. Well, this year, the latest and greatest spec is 240Hz, which is supposed to do what 120Hz does, but better.
Not too long ago, our video guru David Katzmaier gave his initial impressions on 240Hz in a post titled "Is 240Hz worth waiting for?" When he wrote that piece, he'd just seen his first 240Hz TV in action and wasn't sold on the new technology. Now that he's reviewed four 240Hz HDTVs and has a fifth review (the LG 47LH55) in the works, he's still not sold, but he admits the verdict isn't totally clear-cut.
Part of the problem is that there's a difference between what your eye sees in everyday material you watch and objective testing done with test patterns. As Katzmaier notes in his post, "Standard LCD and plasma TVs refresh the screen 60 times per second, or 60Hz, which is plenty fast enough to eliminate flicker and create the illusion of motion from a series of still images. In fact, most sources sent to your display arrive at the nominal rate of 30 frames per second, and each frame is repeated once by the television to achieve 60 total fps."
For most people, including me and Mr. Katzmaier, it's very difficult to see the impact that "faster" LCD sets have on picture quality. We spent some time in our AV lab watching various source material from 120Hz TVs and 240Hz models and it's really hard to detect any difference (it's hard to detect any difference between 120Hz and 60Hz models, too). To be clear, I'm referring here to motion-blur reduction because of faster refresh rates, not to dejudder processing, which smooths out motion and makes film-based material shot at 24fps look more video-like. When dejudder is engaged, you can easily spot its impact on the picture. (It's also worth mentioning that the dejudder processing on the 240Hz TVs we tested so far wasn't any better--or worse--than than the dejudder on 120Hz TVs).
... Read moreEventually, of course, manufacturers will completely phase out 720p TVs. But it may take a few years. While the number of new 720p models is dwindling, several manufacturers, including Sony, Samsung, LG, and Panasonic, are putting out entry-level lines in 2009 that feature 720p TVs and we're getting a lot of readers asking whether they should save some dough and buy them. With that in mind, here's the word on 720p vs. 1080p, updated for this year.
1. What's so great about 1080p?
1080p resolution--which equates to 1,920x1080 pixels--is the current Holy Grail of HDTV resolution. That's because most 1080p HDTVs are capable of displaying every pixel of the highest-resolution HD broadcasts. They offer more than twice the resolution of step-down models, which are typically 1,366x768, 1,280x720, or 1,024x768. These days, HDTVs with any of those three of lower resolutions are typically called "720p." Nobody wants to remember all those numbers, and "768p" doesn't really roll off the tongue.
2. How much extra does a 1080p TV cost?
When I wrote my original article a few years ago, you had to pay a premium of about $1,000 to get a 1080p model at the same screen size as a "720p" set. While the gap has certainly narrowed, there's still a notable difference. In the case of a 32-inch LCD, for instance, you're looking at around a $200-$250 price bump. For example, the Samsung LN32B360 goes for $549.99, while the step-up 1080p version, the LN32B530, goes for $799.99. Sony has a similar price delta when it comes to its 32-inch LCDs.
As you move up the LCD-size chain, your 720p options basically disappear. Samsung and Sony, the two biggest names in LCD, don't even produce 720p LCDs larger than 32 inches anymore. You can still find older big-screen 720p models, like the 40-inch Samsung LN40A450, but they're becoming a rare breed.
This Panasonic 50-inch 720 plasma costs much less than the 1080p step-up model.
(Credit: Panasonic)When it comes to plasma, Panasonic's entry-level 42-inch TC-P42X1 720p carries a price of around $899.99, while the step-up 1080p version, the TC-P42S1, come in at $1,199.99 (street prices will vary, of course). Move up to Panasonic's 50-inch models and you're looking at more like a $700 delta, with the 720p TC-P50X1 coming in around $1,000 and the TC-P50S1 selling for $1,700--though Panasonic's S1 series does feature more-efficient, higher-contrast NEO-PDP panels. (Note: We do expect prices to drop slightly on all these models as the year progresses).
3. Why is 1080p theoretically better than 1080i?
1080i, the former king of the HDTV hill, actually boasts an identical 1,920x1,080 resolution, but conveys the images in an interlaced format (the i in 1080i). In a tube-based television, otherwise known as a CRT, 1080i sources get "painted" on the screen sequentially: the odd-numbered lines of resolution appear on your screen first, followed by the even-numbered lines--all within 1/30 of a second. Progressive-scan formats such as 480p, 720p, and 1080p convey all of the lines of resolution sequentially in a single pass, which makes for a smoother, cleaner image, especially with sports and other motion-intensive content.
... 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 more
If the picture doesn't pop, it's not HD.
(Credit: CNET Australia)
"Dude, what do you think? Pretty good, huh? I got the one you guys [CNET] recommended."
I look at the TV and there seems to be something a little off about it. I move closer and say:
"You have HD?"
"Yeah," he replies, pointing to the cable box sitting underneath the TV.
I tell him to turn it to an HD channel. Something in the 700s (the HD channels for Time Warner Cable in New York are all in the 700s).
"I have it on an HD channel."
For good measure, I have him turn to 702, CBS HD. (Now that we're owned by CBS, I always tell people to go to CBS HD first. Naturally.)
"Dude," I say, "You're not watching HDTV."
"I'm not?"
"No, you are not."
On New Year's Eve, I was dealing with a Sony Bravia. About 3 years old. Cosmetically, really good looking. It wasn't displaying HD, however, even though there was an HD box sitting right next to the TV.
I took a quick look at the box's rear and lo and behold, there was a yellow composite video cable running from the back of the cable box to the back of the TV. Sound was carried by the standard red/white composite cables.
"I hate to break it to you," I said to my host (I didn't say dude because he was a buttoned-up dude who you don't call dude), "but you're running video to your expensive TV through the worst possible video connection."
This was actually the fourth time I'd encountered just such a scenario in the last couple of years. Three times the owner had screwed up and in the fourth instance, a "professional" installer had--remarkably--hooked my friend's system up with a composite video cable. (Shame on my friend; double shame on the installer).
In this case, part of the problem was that the cable box was fairly old and had a DVI connection but no HDMI. That meant the owner would have had to purchase a DVI-to-HDMI cable, then run the sound to the TV with the red/white composite cables (he didn't have an AV receiver in the mix). For a lot of people, that's just too complicated. Of course, today all new satellite and cable HD boxes feature HDMI connections, which makes things much simpler if all you're looking to do is hook your set-top box up to the TV and get HD video and stereo sound through your TV's speakers. But somehow people occasionally manage to screw that up, too. (Watch our "How to connect high-def to your HDTV" explanation here).
Anyway, to make a long story short, in the middle of the party I magically turned the composite cable into component cables (no, the colors don't match up, but in a pinch you can always convert the yellow/white/red composite cable into a red/blue/green component cable) and pumped the HD into the set that way. The sound had to be passed through a separate red/white composite cable, but people always tend to have an extra set of those lying around, so we were cool there.
I then fiddled around with the cable box's video-output settings and the Sony's settings until everything was how it was supposed to be (at least in terms of getting the pictured displayed at the proper aspect ratio and resolution). Unfortunately, a lot of this stuff is still too complicated for the average person to deal with (and sound is a whole other matter entirely).
When I finally got the HD working, the small crowd erupted in applause and the owner of the TV stood back and looked at the set, stunned. I was briefly Moses parting the Red Sea.
Alas, I think this situation is more prevalent than I initially thought. I had guessed that around 10 percent of HDTV owners weren't actually watching HD. But it may very well be closer to the 20 percent the LRG survey cites.
What do you guys think? Anybody willing to admit to being an embarrassing victim of the think-you-have-HD-but-you-really-don't syndrome? (Or maybe you're just worried you have it and need advice). And has anyone helped save a friend with an HDTV afflicted with non-HD syndrome?
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