Version: 2008
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LED TVs compared: Local dimming versus edge-lit

David Katzmaier David Katzmaier, Senior Editor October 28, 2009


If you thought all LCD 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 have introduced numerous new technologies, but the most successful in our opinion is LED backlighting with local dimming. When you see the words "LED TV" in an ad, it definitely refers to an LCD TV, but there's no guaranteeing that local-dimming technology is also onboard.

Before we get too far ahead of ourselves, we need to explain some basic concepts. All LCD-based TVs rely on a backlight of some kind to illuminate the LCD panel itself. Most use fluorescent backlights, known as CCFL, but a growing number of sets use LED backlights instead. LEDs use less power, but their main picture quality advantage is the capability to deliver deep black levels that rival and in some circumstances surpass those of the best plasma sets.

There are two major versions of LED backlights illuminating today's LCD TVs. One is called local dimming, found on sets such as the Samsung 8500, the LG LH90, the Toshiba SV670, and the Vizio VF551XVT, that lets the backlight dim or turn off in different areas across the screen (more information). Edge-lit, the other version, is found on sets such as the Samsung B8000 models, and it gets its name from the arrangement of the LEDs along the edge of the screen, allowing for extremely thin cabinet designs (check out the slideshow). A third version is also available, but from only one manufacturer so far. Sharp's LC-LE700UN series uses LED backlights without local dimming that are arranged behind the screen instead of along the edge. In the Sharp's case, the LEDs don't have much on an impact on picture quality.

In our tests, we liked local dimming best of the three backlighting methods, and rank the so-equipped TVs below among the best LCDs we've ever reviewed. In comparison, the edge-lit models exhibited relatively poor uniformity and backlight fluctuations that can definitely be distracting--although a new firmware update by Samsung is aimed at correcting this issue. On the other hand, they're pretty good performers in their own rights--just not in the same league, so far, as the local-dimming models. For what it's worth, we still consider the best plasma TVs better overall performers than even local-dimming LCD displays, although Samsung's new 8500 series comes mighty close.

We're looking forward to testing more LED-based LCD models, including Sony's KDL-XBR10 series and LG's SL90 series before the end of the year.

More Resources
LED TVs: 10 things you need to know,
Best LED TVs,
LED-backlit LCDs of 2008: local dimming,
Samsung reveals its edge-lit LED-based LCDs,
Samsung LED TV ads called 'misleading'
Product name
Price $2,398.52 to $3,599.98 $1,699.99 to $1,999.95 $1,315.99 to $2,499.99 $2,049.00 to $2,204.12 $1,249.95 to $1,999.99 $1,879.00 to $2,499.99
CNET editors' rating
Average user rating 0 stars 0 stars
Review date October 06, 2009 July 10, 2009 August 27, 2009 October 23, 2009 October 16, 2009 September 25, 2009
The Bottom Line It costs a mint, but Samsung's local dimming, LED-based UNB8500 series delivers the best picture quality of any LCD we've tested. Deep black levels and accurate color help propel the LED-backlit LG LH90 series into the front row of the LCD picture quality class. Albeit slightly less impressive than other LED-based LCDs with local dimming, the Toshiba SV670U also costs less and still gives great blacks. Sure, it has a few flaws, but nothing fatal prevents the local dimming, LED-backlit Vizio VF551XVT from exhibiting excellent LCD picture quality for the buck. The Sharp LC-LE700UN's LED backlighting doesn't elevate its picture quality beyond the LCD norm, but does help make it the most efficient TV we've ever tested. The expensive, stylish Samsung UNB8000 series has its share of picture quality drawbacks, but a firmware update helps, and the thin frames are worth serious bragging rights.
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Features
Input Video FormatsInfo unavailable720p
1080i
1080p
1080/24p
1080/30p
1080/60p
1080p
480i
480p
720p
1080i
1080p
1080p
1080p
Digital TV TunerQAM
ATSC
QAM
ATSC
QAM
ATSC
QAM
ATSC
QAM
ATSC
QAM
ATSC
HDMI Ports Qty4
4
4
5
Info unavailable4
USB PortYes , 2 port(s)
Yes , 1 port(s)
1 port(s)
Yes
Yes
Yes , 2 port(s)
Resolution1920 x 1080
1920 x 1080
1920 x 1080
1920 x 1080
1920 x 1080
1920 x 1080
Motion Enhancement TechnologyAuto Motion Plus 240Hz
TruMotion 240Hz
ClearScan 240
240 Hz Smooth Motion technology
Info unavailableAuto Motion Plus 240Hz
Sound Output ModeStereo
Surround Sound
Stereo
Stereo
Stereo
Stereo
Speaker System2 speakers
4 speakers
2 speakers
2 speakers
Info unavailable2 speakers
RadioNone
None
None
None
None
None
Environmental StandardsYes
Yes
Yes
Yes
Yes
Yes
DVDNone
None
None
None
None
None
Dimensions (WxDxH)Info unavailable46.5 in x 15.7 in x 33.6 in - With stand
45.7 in x 4.4 in x 28.5 in - Without stand
51.6 in x 5 in x 33.9 in - Without stand
43.3 in x 13.9 in x 29.3 in - With stand and speakers
44.5 in x 10.9 in x 29.8 in - With stand
BatteryNone
None
None
None
None
None
Remote ControlRemote control - Infrared
Universal remote control - Infrared
Universal remote control - Infrared
Universal remote control - Infrared
Info unavailableRemote control - Infrared
VCRNone
None
None
None
Info unavailableNone
TechnologyTFT active matrix
TFT active matrix
TFT active matrix
TFT active matrix
TFT active matrix
TFT active matrix
Diagonal Size46 in - Widescreen
47 in - Widescreen
46 in - Widescreen
55 in - Widescreen
46 in - Widescreen
46 in - Widescreen
Digital Television CertificationHDTV
HDTV
HDTV
HDTV
HDTV
HDTV
Progressive ScanProgressive scanning (line doubling)
Progressive scanning (line doubling)
Progressive scanning (line doubling)
Progressive scanning (line doubling)
Progressive scanning (line doubling)
Progressive scanning (line doubling)
HDCP CompatibleYes
Yes
Info unavailableYes
Yes
Yes
Display Format1080p
1080p
1080p
1080p
1080p
1080p
LCD Backlight TechnologyLED Backlight technology
LED Backlight technology
LED Backlight technology
LED Backlight technology
LED Backlight technology
LED Backlight technology
PC InterfaceVGA (HD-15)
USB
VGA (HD-15)
HDMI
VGA (HD-15)
HDMI
VGA (HD-15)
VGA (HD-15)
USB
VGA (HD-15)
Video InterfaceHDMI
Component
HDMI
Component
Composite
HDMI
S-Video
Component
Composite
HDMI
S-Video
Component
Composite
HDMI
S-Video
Component
Composite
HDMI
Component
Product DescriptionSamsung UN46B8500 - 46 in LCD TV
LG 47LH90 - 47 in LCD TV
Toshiba 46SV670U - 46 in LCD TV
VIZIO VF551XVT - 55 in LCD TV
Sharp LC 46LE700UN - 46 in LCD TV
Samsung UN46B8000 - 46 in LCD TV
Product TypeLCD TV
LCD TV
LCD TV
LCD TV
LCD TV
LCD TV
Full specifications Full specifications Full specifications Full specifications Full specifications Full specifications Full specifications
Buying choices