There are 3 main types of
LED TVs:
Edge-lit: LEDs are arranged around the perimeter of the screen and lit is distributed via a diffusive reflection panel behind the LCD screen. It has only slight advantage in picture quality over CCFLs but it produces the thinnest of all the
LCD TVs. (All Samsung LEDs 8000 series and below.)
Back-lit: An array of LEDs are arranged directly behind the LCD screen. The LEDs can be dimmed but not independently. Brighter pictures and more energy efficient than CCFL but not as thin as Edge-lit. (Sharp LE700 series.)
Local-dimming: Local dimming is Back-lit but individual or small groups of LED's can be dimmed independently. This is the most expensive but it produces the richest colors and the deepest blacks. Again, not as thin as Edge-lit but close to plasma in terms of contrast ratio. Local dimming comes in two varieties; all-white LEDs or groups of red, green, & blue LEDs. (Samsung 8500 series and Sony XBR8 Tri-Luminous)
An important thing to note is that just because an LED is backlit does not mean there is an LED for each pixel. Actually, no such TV exists. In the case of the
Sharp LE700, there is only a couple dozen LEDs behind the whole LCD screen. Usually, one LED is responsibly for lighting several thousands of pixels. Which means there is still room for improvement as LEDs get smaller and less expensive.
The biggest thing to remember about LED TVs is that they offer a better picture than CCFL, they are more energy efficient (by up to 40%) and the are usually thinner.
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