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LED TVs compared: Local dimming, edge-lit, and full array
David Katzmaier
Senior editor July 7, 2010 (updated on: July 8, 2011)
If you thought all LED TVs were created equal, you're underestimating the power of confusion as a marketing tool. In their continuing efforts to compete against the picture quality advantages of plasma-based flat-panel TVs, makers of LCDs TVs have introduced numerous new technologies. The most successful in our opinion is full-array LED backlighting with local dimming. When you see the words "LED TV" in an ad, it definitely refers to an LCD TV with an LED backlight, but what type of LED backlight and how it's configured make all the difference.
Below we've gathered reviews of six different "LED TVs" that provide examples of all four LED backlight configurations, but first we'll provide a bit of context. All LCD-based TVs rely on a backlight of some kind to illuminate the liquid-crystal panel itself. The most common use fluorescent backlights, known as CCFL, but a growing number feature LED backlights instead. LEDs use somewhat less power, can enable thinner flat-panel cabinets, and--crucially for TV makers--provide a great excuse to charge more money. But make no mistake: despite the misleading marketing, LED TVs are just LCD TVs with fancy backlights.
Unfortunately for TV shoppers, the confusion just increases from there. To help cut through the clutter we're going to lengthen our descriptions beyond the "LED TV" shorthand, and tell you how picture quality generally compares with standard LCD. More details are available in our LED TVs: 10 things you need to know companion piece as well as the individual reviews.
Full-array without local dimming: The rarest of the bunch but the most familiar in concept. These models are just like standard LCD-based TVs aside from the fact that the CCFL backlight is replaced by LEDs. The "full-array" means that the LEDs themselves are arranged behind the entire LCD panel, not just along the edge.
Picture quality impact: No difference compared with standard LCD.
Example below: Sharp LC-70LE73U series
Edge-lit without local dimming: The most common today. Chances are if you see an "LED TV" advertised, it's this variety, which was first widely introduced by Samsung in 2009, then imitated in the last two years by just about everyone else. It's characterized by thin cabinet designs--around just an inch or even less in depth--that lead to decreased weight in shipping and wall-mounting, along with increased bragging rights (although we fail to see much practical appeal versus a standard, 3-to-5-inch-deep flat-panel TV). Unlike full-array models, the LEDs on these sets are arranged only along the edge of the LCD panel, and can illuminate the center and other areas of the screen using so-called "light guides."
Picture quality impact: No major advantage over standard LCD, and can have even more uniformity problems, such as brighter edges compared with the middle.
Example below: Samsung UND6400 series
Full-array with local dimming: The original and still the best. There are exceptions, but in general, TVs with this LED backlight configuration are the best-performing LCDs you can buy. They're similar to full-array models, but the individual zones of LEDs can be dimmed or brightened independently.
Picture quality impact: Can have significantly better black levels and uniformity than normal LCD, but will also exhibit "blooming," or stray illumination, to some extent.
Examples below: Vizio XVT3 series; Sony XBR-HX929 series
Edge-lit with local dimming: A hybrid currently available on select models from Samsung, LG, and Sony. The idea is to allow some dimming of the screen in independent areas without having to place LEDs behind the LCD panel, just along the edge.
Picture quality impact: In our tests of the TVs here, the Samsung achieved darker black levels than the best nondimming edge-lit model (the UND6400), and the LG matched it, but neither matched the picture quality of full-array with local dimming and both exhibited more blooming.
Examples below: Samsung UND8000 series; LG LW5600 series
More resources: LED TVs: 10 things you need to know; Best LED TVs
The products listed below represent one screen size in one series of TVs from each maker. Click through to the reviews for more size options.
| Product name | ||||||
|---|---|---|---|---|---|---|
| Price | $1,590.00 to $2,864.32 | $1,149.00 | Check Prices | $2,499.00 to $3,357.31 | $1,589.00 to $2,400.00 | $1,699.94 |
| CNET editors' rating | ||||||
| Average user rating | ||||||
| Release date | July 27, 2011 | March 15, 2011 | August 15, 2010 | June 15, 2011 | March 01, 2011 | April 01, 2011 |
| The Bottom Line | For people craving a colossal flat-screen TV who don't want a plasma or a projector, the 70-inch Sharp LC-70LE73U series LED-based LCD offers very good picture quality, especially in bright rooms. | Solid overall 2D and 3D picture quality, as well as a wealth of features and beautiful looks, mark the Samsung UND6400 as one of the better edge-lit LED-based LCD TVs we've tested. | The Vizio XVT3SV series' excellent picture quality, thoughtful design, scads of features, and reasonable price combine to make it the best value among high-end LED-based LCD TVs today. | One of the best-performing LED-based LCDs we've ever tested, the expensive local-dimming Sony XBR-HX929 competes well with the top plasmas. | The Samsung UND8000 TV delivers best-in-class looks and features, but its picture quality--thanks to uneven screen uniformity--is ultimately not as good as that of many less expensive models. | While passive 3D has its flaws, the LG LW5600's 2D picture quality is very good for an edge-lit LED-based LCD TV, especially in bright rooms. |
| Features | ||||||
| Surround mode | Info unavailable | Yes | Yes | Yes | Yes | Yes |
| Sound effects | Info unavailable | SRS TheaterSound HD | SRS StudioSound HD | S-FORCE Front Surround 3D | SRS TheaterSound | Infinite 3D Surround |
| Addtional features | Quattron Quad Pixel Technology AQUOS Advantage X-GEN panel AQUOS LINK UltraBrilliant LED System Vyper Drive Digital Still Picture Display Quad Pixel Plus | Auto Volume Leveller (AVL) Bottom mounted | SRS TruVolume | Corning Gorilla Glass panel X-Reality PRO Engine Eco Drive Clear Voice technology Alternate Audio Sound Enhancer Invisible Speaker System S-Master Digital Amplifier Game mode Sleep timer | AllShare DLNA networking Auto Volume Leveller (AVL) Ultra clear panel | Auto Volume Leveller (AVL) Clear Voice II technology |
| Input/Output connections | 4 x HDMI input (19 pin HDMI Type A) 1 x HD component input (RCA phono x 3) 1 x Composite video input (RCA phono) Audio line-in (RCA phono x 2) 1 x Serial 1 x VGA input (15 pin HD D-Sub (HD-15)) 1 x Network (RJ-45) USB (4 pin USB Type A) | 4 x HDMI 3 x USB (19 pin HDMI Type A) - Rear (RCA phono x 3) - Rear (Mini-phone stereo 3.5 mm) (4 pin USB Type A) (RCA phono x 2) (15 pin HD D-Sub (HD-15)) (RCA phono) (Mini-phone stereo 3.5 mm) (TOSLINK) | 5 x HDMI input (19 pin HDMI Type A) 1 x Antenna (F connector) - Rear 1 x Composite video/audio input (RCA phono x 3) - Rear 1 x Component video input (RCA phono x 3) - Rear 1 x Audio input (RCA phono x 2) - Rear 1 x VGA input (15 pin HD D-Sub (HD-15)) - Rear 1 x Ethernet (RJ-45) - Rear 3 x USB (4 pin USB Type A) 1 x SPDIF output (TOSLINK) - Rear 1 x Audio output (RCA phono x 2) - Rear | 1 x Composite video input (RCA phono) - On supplied adapter 1 x Composite video / component video input (RCA phono x 3) - On supplied adapter 2 x HDMI input (19 pin HDMI Type A) - Bottom 2 x HDMI input (19 pin HDMI Type A) - Side 1 x VGA input (15 pin HD D-Sub (HD-15)) - Side 1 x Audio line-in (Mini-phone stereo 3.5 mm) - Side 2 x Audio line-in (RCA phono x 2) - On supplied adapter 1 x Digital audio output (optical) (TOSLINK) - Side 1 x Audio line-out / headphones (Mini-phone stereo 3.5 mm) - Side 2 x USB 2.0 (4 pin USB Type A) - Side 1 x Network (RJ-45) - Bottom 1 x Serial - Bottom | 4 x HDMI 3 x USB (19 pin HDMI Type A) (RCA phono x 3) (4 pin USB Type A) (15 pin HD D-Sub (HD-15)) (TOSLINK) (Mini-phone stereo 3.5 mm) (RCA phono x 2) (Mini-phone stereo 3.5 mm) (RJ-45) | 1 x VGA input (15 pin HD D-Sub (HD-15)) - Rear 1 x Serial - Rear 4 x HDMI input (19 pin HDMI Type A) - Side 2 x Composite video/audio input (RCA phono x 3) - Rear 1 x Headphones (Mini-phone stereo 3.5 mm) - Rear 1 x Audio line-in (Mini-phone stereo 3.5 mm) - Rear 1 x Digital audio output (optical) (TOSLINK) - Rear 2 x USB 2.0 (4 pin USB Type A) - Side 2 x Component video input (RCA phono x 3) - Rear 1 x Network (RJ-45) - Rear 1 x Audio line-in (RCA phono x 2) - Rear |
| Total output power | 20 Watt | 20 Watt | 30 Watt | 30 Watt | 20 Watt | 20 Watt |
| Weight | 121.3 lbs | 29.8 lbs | 77.2 lbs | 57.5 lbs | 35.7 lbs | 40.8 lbs |
| Image aspect ratio | 16:9 | 16:9 | 16:9 | 16:9 | 16:9 | 16:9 |
| Digital TV tuner | ATSC QAM | ATSC QAM | ATSC QAM | ATSC QAM | ATSC QAM | ATSC QAM |
| Diagonal size | 70 in | 46 in | 55 in | 55 in | 55 in | 47 in |
| Technology | LED-LCD | 3D LED-LCD | TFT active matrix | 3D LED-LCD | LED-LCD 3D | 3D LED-LCD |
| HDMI ports qty | 4 | 4 | 5 | 4 | 4 | 4 |
| Speaker(s) | 2 x Right/left channel speaker - Built-in - 10 Watt | 2 x Main channel speaker - Built-in - 10 Watt | 2 x Right/left channel speaker - Built-in - 15 Watt | 2 x Speaker - 10 Watt 1 x Subwoofer - 10 Watt | 2 x Right/left channel speaker - Built-in - 10 Watt | 2 x Right/left channel speaker - Built-in - 10 Watt |
| Resolution | 1920 x 1080 | 1920 x 1080 | 1920 x 1080 | 1920 x 1080 | 1920 x 1080 | 1920 x 1080 |
| Sound output mode | Stereo | Stereo | Stereo | Stereo | Stereo | Stereo |
| Product type | LED-LCD | LED-LCD | LED-LCD | LED-LCD | LED-LCD | LED-LCD |
| Dimensions (WxDxH) | 63.4 in x 14.2 in x 39.8 in - With stand | 41.7 in x 1.2 in x 24.5 in - Without stand | 52.4 in x 13 in x 35.2 in - With stand | 50.4 in x 1.5 in x 30.4 in - Without stand | 48.4 in x 1.2 in x 27.8 in - Without stand | 44.1 in x 1.2 in x 26.9 in - Without stand |
| Dynamic contrast ratio | 8000000:1 | 5000000:1 | 10000000:1 | Info unavailable | 25000000:1 | 8000000:1 |
| Manufacturer warranty | 1 year warranty | 1 year warranty | 1 year warranty | 1 year warranty | Info unavailable | 1 year warranty |
| LED backlight type | Full array | Edge Light w/ local dimming | Full array | Full-array with local dimming | Edge-lit | Edge Light with local dimming |
| Refresh rate | 120 Hz | 120 Hz | 240 Hz | 240 Hz | 240 Hz | 120 Hz |
| HDCP compatible | Yes | Yes | Yes | Yes | Yes | Yes |
| Widescreen | Widescreen | Widescreen | Widescreen | Widescreen | Widescreen | Widescreen |
| Display format | 1080p | 1080p | 1080p | 1080p | 1080p | 1080p |
| LCD backlight technology | LED Backlight technology | LED Backlight technology | LED Backlight technology | LED Backlight technology | LED Backlight technology | LED Backlight technology |
| Connectivity protocols | Built-in Wi-Fi | Bluetooth | IEEE 802.3 (Ethernet) IEEE 802.11n | Built-in Wi-Fi IEEE 802.11n | Built-in Wi-Fi | Wi-Fi ready, adapter included |
| TV tuner presence | Yes | Yes | Yes | Yes | Yes | Yes |
| PC interface | VGA (HD-15) | VGA (HD-15) | VGA (HD-15) | VGA (HD-15) | VGA (HD-15) | VGA (HD-15) |
| Video interface | HDMI Component Composite | HDMI Component Composite | HDMI Component Composite | HDMI Component Composite | HDMI Component | HDMI Component Composite |
| Full specifications | Full specifications | Full specifications | Full specifications | Full specifications | Full specifications | Full specifications |
| Buying choices | | | | | ||
Thought of buying LG LE5500 series but going by your reviews, I now think it is not a good idea...Which is the best affordable LED TV in the current market now?
Howz LG LE8500 series?
LED backlights can be dimmed in several ways as he pointed out but the details are off:
1) Just dim the entire backlight to average brightness level of the picture -- this increases the panel effective contrast ratio by about 4:1 so a 1000:1 panel gets to about 4000:1. Since the average brightness level of video and movies is about 25% of max, this also drastically lowers the overall power consumption compared to a non-dimmed standard LCD TV. Easy to do with leds, harder with slow responding CCFLs
2) In edge lit, if lit from the side edges (not top/bottom) you can locally dim horizontal sections (think of outside, the sky is bright, the ground is darker) so that the effective contrast ratio is enhanced on average by 10:1 so now the panel is an effective 10000:1
3) Fully local dimming where a checkerboard of leds behind the panel can be individually dimmed enhances on average about 100:1 if the checkerboard has at least 64 discrete areas and more enhancement with a smaller grid checkerboard. This takes the panel to levels of contrast beyond the unadapted eye dynamic range and can cause some haloing both on the screen and in the eyes of the viewer (look at a bright light, you will see a halo around it)
4) fully local dimmed with individual red/green/blue leds per checkerboard square (instead of just white leds) allows the color range to be greatly expanded beyond the antiquated current broadcast standards and allows a color range approaching the real world -- if any programming were available to use it
But does anyone know whether Samsungs 5000 models have local dimming? And would a smaller TV even matter whether it is full array or Edge lit since the light doesn't have to travel as far?
But does anyone know whether Samsungs 5000 models have local dimming? And would a smaller TV even matter whether it is full array or Edge lit since the light doesn't have to travel as far?
I think that the popularity of LCD's is a result of comparing them with plasmas in the store where there are lots of lights, and the brighter screen will always seem to be better when compared side-by-side, but that does not mean it really is better. There are still issues of backlight uniformity / bleed / blooming / etc, color that changes with viewing angle, motion irregularities, etc that are all side effects of lcd technology. Plasma deserves a serious look.
Thanks
Brain Reavey
Can someone point out where this information would be found in the spec sheets on the tv?
Thanks for the excellent article, but it is not enough, as you see from many of the comments here. Like others I hesitate. I want to spend my few dollars wisely on a 35-42" screen that is a great value. I don't expect cutting edge quality or features, but don't want embarrassing spots, bleeds or ooze. Help me, Obi-wan. Please write chapter 2 of this analysis. Thanks!
You list the Vizio XVT3SV series as a full array local dimming set, but all the info I can find says it uses edge lit technology, like the company site here:
http://www.vizio.com/led-lcd-hdtvs/xvt3d650sv.html?___SID=U
Comments?
Thanks,
RB
1)Sony EX521/46. That is a 46".
Or
2)LG 47LV4400. That is a 47".
Tks for your time.
My original NX711 was a great and even picture. There was no light bleed in the corners. After applying an update last October, it went down. Besides for having to goto the lengths of FAXING Sony corporate offices because I would have their regular support agent lie, change their story, put me on eternal hold when asking for a supervisor, etc. Iv been through five replacements by their so called 'white glove service'. All the sets have had varying degrees of this light-bleed issue described as just part of the edge-lit scenario.
Keep in mind my original unit, which was edge-lit, DID NOT have this light-bleed issue. However, after being contected by their 'Sony Listens' team, which it appears here they do, Iv went through FOUR models that, again, have all had this problem but in different amounts/effects. To me, this states this is happening due to manufacturing. Not the reason described in the article. Maybe thats just Sony's technology though. Others may fit the articles scenario.
This has to be a complete lack of manufacturing standards and decision that we should just be happy to have their brand in our homes. If the light bleeding was consistent, Id agree with the acrticle, but it just isnt so. It varies even in the same model. Hence... production issue, not techonology!