LED - Explained

http://www.youtube.com/watch?v=Og6_ABWMsR4&feature=related

If you thought all LCD TVs were created equal, you're underestimating the power of confusion as a marketing tool.  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 & the other called Edge-lit (which gets its name from the arrangement of the LEDs along the edge of the screen, allowing for extremely thin cabinet designs) . A third version is also available, but from only one manufacturer so far. Sharp 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 (CNET), we liked local dimming best of the three backlighting methods, and rank the so-equipped TVs 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.. 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.