LED vs. LCD display screens

[Cyclops]

LED TVs are technically a member of the LCD TV family. The display screen on a LED is a liquid crystal display the same as it is on any other LCD TV. The main difference between the two lies with different backlighting techniques which may change the picture quality characteristics dramatically.

Traditional LCDs have used some form of flourescent lighting from tubes to much more advanced flat arrays of lights. LED TVs use Light Emitting Diodes to light the LCD panel. Just as there are different styles of flourescent lights in traditional LCDs there are also different styles of LED backlighting. There are LED TVs like the Sony KDL-55XBR8 (see review) that have a panel of LED lights behind the LCD panel. In the Sony the LEDs are tri-colored and can be controlled in banks for an effect called "local dimming". This allows darker areas of the picture to have the backlighting dimmed behind them resulting in better contrast and black levels. In the Luxia line of Samsung LED TVs, the LED lights are surrounding the edge of the panel and this arrangement allows for the very slim depth of those models. Without the ability to do local dimming these are functionally similar to traditional LCDs so in this article we will be comparing local dimming LED TV to traditional LCD TV.

PICTURE CONSIDERATIONS

CONTRAST / BLACK LEVELS

Traditional LCD televisions always have their backlight on when the TV is on. To create black or dark areas the screen must block the light by twisting the crystals to a closed position, often resulting in a lower contrast ratio and less detail in dark areas of the picture. This is a shortcoming in LCD technology that LED TVs with local dimming are attempting to correct. With the controlled backlighting the LEDs can be dimmed in dark areas of the picture to create darker blacks and better detail in dark scenes.

ADVANTAGE: Local dimming LED TV technology has a clear advantage in contrast and black levels.


COLOR ACCURACY

With white LED backlights the difference between the two technologies isn't very significant, but with RGB colored lights or a color wheel to affect the backlight color the LED TVs have an advantage in displaying realistic color.

ADVANTAGE: Without colored LEDs or another way to affect the backlight color these two technologies are nearly equal. With colored backlighting LED TV takes the advantage


VIEWING ANGLES

While traditional LCDs have improved their useable viewing angles over the years this is still a shortcoming of the technology itself and even the best LCDs will suffer from contrast degradation when viewed from angles wider than around 30 degrees off center. The LED backlit LCDs we've seen have done a fantastic job of correcting this issue and have viewing angles that rival plasma TVs (but at a much higher price).

ADVANTAGE: LED TV


FUNCTIONAL CONSIDERATIONS

COMPUTER USE

LCD technology of either sort is immune to screen burn-in so they are equally well suited for computer use.

ADVANTAGE: Even.


FAST-MOVING VIDEO PLAYBACK

Displaying fast moving video is a function of the response time and refresh rate in LCD and LED televisions. The type of backlighting in the TV has no effect on the reproduction of fast moving video. You will want to compare response times and refresh rates when making a purchase decision.

ADVANTAGE: Even


LONGEVITY

Most manufacturers are claiming approximately 100,000 hours lifetime for their televisions. LED backlit televisions are brand new and don't have much of a track record but LED lights are typically long lived.

ADVANTAGE: LED televisions do not have much history. They should have an advantage since the flourescent style backlighting used in traditional LCDs ever so slightly change color hue over time. Light emitting diode technology should not have as much degradation over time. Quality of manufacture for either technology will also matter.


OTHER CONSIDERATIONS

PRODUCTION SIZE AND COST

LED backlight televisions are currently available in sizes ranging from 46 inches to 70 inches. Traditional LCD televisions are available in sizes as small as 15 inches and as large as 65 inches. When comparing LED TVs and traditional LCDs in the same size the LED backlit model will be more expensive, in some cases vastly more expensive.

ADVANTAGE: There is certainly a much larger number of LCD TVs being produced today, with LED televisions demanding a premium for the often better picture quality.


POWER CONSUMPTION

The LED TVs we've come across have used quite a bit more power than a traditional LCD TV in the same screen size. LED TVs approach plasma displays in power usage.

ADVANTAGE: LCD