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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.

Edge-lit LED-based LCD by Samsung explodes--photos

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

The photoshopped screen in this picture betrays its true nature. The real screen is glossy--real glossy.

(Credit: Josh P. Miller/CNET)

The LED revolution has truly begun. In the last month or so, we've reviewed three LED-based LCD computer monitors, and we expect that they won't be the last.

AOC V22 photos

Last week, we looked at the LG Flatron W2386L. It's an LED-based monitor that, while offering great game performance and a thin design, could not compare performancewise to the current LED king, the Samsung SyncMaster XL2370.

This week, we reviewed the AOC V22 LED monitor. Unlike many recent monitors, this one has a 16:10 aspect ratio instead of 16:9, Also, it has an extremely glossy screen--like "I can pick food out of my teeth looking at this thing" glossy.

More monitor reviews can be found here.

Samsung's UNB8500 series costs a bundle.

(Credit: Sarah Tew/CNET)

If you watch football or read CNET, chances are you've noticed ads for Samsung's so-called LED TVs. The company has released three series of these super-thin LED-based LCDs so far this year, the 6000, 7000 and 8000 models, but it's saved the best for last. The fourth series is dubbed UNB8500, but you can remember it best as the king of LCD--for now.

Unlike the other three Samsung models, which use LED elements arranged along the edge of their screens, the company's two 8500 models employ a full array of local dimming LEDs behind the screen, yet maintain an ultraslim profile. As a result this expensive HDTV handily outperforms its brothers and, yes, every other LCD-based display we've ever tested. It still can't match the best plasma, the legendary and discontinued Pioneer Kuro, and its off-angle picture leaves plenty to be desired, but people who claim the sweet spot in front of a Samsung UNB8500 will be treated to the most impressive flat-panel picture quality of the year.

Read the full review of the Samsung UNB8500 series.

Samsung UNB8500 series--photos

The Sony KDL-55XBR8 is officially the best LCD TV CNET has ever tested. It can't overcome the picture quality advantages of the best plasma, however, and it still costs a mint.

The $7,000 Sony KDL-55XBR8 gives great picture.

(Credit: CNET)

We described the battle for "best" between hyperexpensive LED-backlit LCD televisions previously, and in our review of the Sony we compared it directly with the Samsung LN46A950, its principal LCD competitor, as well as to the best HDTV we've ever tested, the Pioneer PRO-111FD plasma. The Sony outperformed the Samsung in most important areas, namely black-level performance, but it exhibited the same sort of off-angle issues and minor "blooming," where black areas become slightly brighter near very bright areas of the screen. Still, Sony's "Triluminos" LED technology seems give it the upper hand over the Samsung in these areas, and its picture is still downright stunning. In fact, in rooms with lots of ambient light the Sony will trounce even the Pioneer Kuro.

Read the full review of the Sony KDL-55XBR8.

... Read more

The spotlight may have been on MacBooks at Tuesday's Apple press conference, but there was one other product on the stage: Apple's new 24-inch Cinema Display.

Admittedly, a monitor is hardly as exciting as an aluminum MacBook, but I do find myself intrigued. The 24-inch display is Apple's first with LED backlighting, which is not only thinner but also reportedly produces more accurate colors while using less energy than traditional monitors. It incorporates an iSight camera, built-in microphone, and speakers. And it includes a second cable at the rear of the display with branches for a MagSafe adapter, USB, and mini-DisplayPort connector.

This last feature is what appeals to me most; combined with three USB ports on the back of the display, it turns the display into a de facto dock for the MacBook and MacBook Pro. The end result is just one cord on your desk, and no more than three connections to unplug when you leave.

Of course, as Apple has shown us time and again, simplicity like that doesn't come cheap: the 24-inch Cinema Display costs $899. To quote CNET Labs' Eric Franklin, "There is no way a 24-inch monitor is worth 900 dollars." Indeed, the HP w2408h is just $500 at HP.com, and Dell currently sells the UltraSharp 2408WFP for $619 on its site. Even the Lenovo ThinkVision L2440x, which also uses LED backlights, costs $750.

So is the unified look and docking function of Apple's 24-inch Cinema Display worth the extra dough? You'll have a little time to decide, because it doesn't start shipping until November.

For complete coverage of the Apple notebook news, see "Apple polishes up its MacBook line."

Thank goodness for the World Police!

(Credit: Paramount Pictures)

First up, Dong is a little concerned that Eric may be a terrorist. He soon discovers, though, that everyone is a terrorist.

Then, LED vs. CCFL LCD backlights. Which makes your eyes bleed less? Find out!

Could our love affair with the iPhone 3G be over? Possibly. Then why do we still own one? It's a complicated answer that we tackle.

Finally, we tell some stories about our early WoW days. Enjoy the fun!

To subscribe to this podcast, visit us at our main page and click the link on the right. Don't forget to leave us a voice mail at 1-800-947-6399 or e-mail us at insidecnetlabs@cnet.com.

When Lenovo announced its ThinkVision L2440x LCD a couple weeks back, I wrote that I was excited about getting it in and testing it. After receiving it last week, I've only completed some preliminary anecdotal testing, but I wanted to write about some quick impressions I got from the monitor.

What I was most excited about was the monitor's LED backlight. LED backlights on LCDs are kind of the new hotness these days. While most LCDs use Cold Cathode Fluorescent Tubes for their backlights, monitors that use LED backlights are known to have better color accuracy and a much longer--about 3:1--lifespan than CCFL-based monitors. They are also purported to be more energy efficient than typical LCDs, although we've yet to actually test this.

(Credit: Eric Franklin/CNET Networks)

As for picture quality, so far, the left and right viewing angles are OK, but not as good as I would have liked. When I moved about 20 degrees to the left or right, I noticed that the picture became noticeably darker; however, text was still readable.

The lower viewing angle was less impressive. At only about 10 to 15 degrees below center, the screen gets a very dark patch at the top. So if you're slouching in your seat while Web surfing or gaming, be prepared that detail on the screen will be harder to see. I mean, I guess you could always just sit up straight, but in my opinion, you shouldn't have to.

When I did sit up straight, while Web surfing and playing World of Warcraft, I noticed that the colors in WoW are vivid without being over-saturated. Everything just had a very smooth and precise look to it--so far. We'll see what I discover once I get down and dirty with the testing.

Design-wise, the display is practical and elegant. I especially like the wide and flat footstand that keeps it from wobbling, and the conveniently placed and comfortable handle that I got some use out of while carrying it around, looking for a spot to photograph it. The screen pivots 90 degrees vertically and rotates nearly 90 degrees to the left and right.

Lenovo is also sending me its ThinkVision L2440p soon and I'd prefer a direct comparison between it and the L2440x, so I won't begin full testing until I have them both in. I'll be testing them in DVI using the Extron Electronics D/2 DA4 Distribution Amplifier that will let me test them simultaneously. Check back in a week or so for full reviews of them both.

We'll hopefully be getting the L2440x soon, as I'm curious to see its LED backlighting in action.

(Credit: Lenovo)

Lenovo announced six new ThinkVision monitors on Wednesday at the Interop 2008 New York, an IT conference and exposition.

• 17-inch L1700p
• 19-inch L1940 Wide
• 19-inch L1940p Wide
• 24-inch L2240 Wide
• 24-inch L2240p Wide
• 24-inch L2440x Wide

According to Lenovo, these monitors use 30 percent to 60 percent less energy than previous ThinkVision models--such as the L171p, L194 Wide, and D221--are EPEAT Gold rated and GreenGuard certified, and include packaging for select models with 65 percent recycled materials.

The ThinkVision L2440x Wide is the flagship of the new lineup and is Lenovo's first 24-inch, low-halogen display that provides up to 225 percent more work area than many 12.1-inch and 13.3-inch ultraportable notebook screens with resolutions of 1,280x800-pixels. The display uses white LED backlighting, which allows it to use only 29 watts of power to operate, according to the EPA Energy Star 4.1 standard it was tested under. To top it off, the display is also mercury and arsenic free. ... Read more

As anybody who pays attention to the ubiquitous Samsung ads that run in CNET's home theater section can tell you, last year I called the picture quality of the company's LN-T4681F a "breakthrough" for flat-panel LCDs. I didn't resort to such highly descriptive language in my review of its successor, the LN46A950, but that doesn't mean I wasn't impressed. It can produce the deepest shade of black of any flat-panel LCD I've reviewed so far.

The extremely expensive A950 series, which also includes a 55-inch version, earns the right to charge so much because it employs LEDs (light-emitting diodes) to create the light behind the screen, whereas most flat-panel LCDs use florescent lights. The difference is that LEDs can be dimmed or turned off in dark areas of the screen.

Last year I noted that the LED-backlit Samsung, while capable of producing some very deep black levels of its own, suffered from some blooming effects--where especially bright objects on dark backgrounds are surrounded by a dim glow--and worse-than average off-angle performance. So did the company correct these issues in its second generation?

Read the full review of the Samsung LN46A950.... Read more