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, Vizio VF551XVT and couple more, that lets the backlight dim or turn off in different areas across the screen another words Local dimming allows LED-backlit sets to produce extremely deep black levels, which are the most important ingredient in HDTV picture quality. The downside, at least in the case of the Samsung, was “blooming,” where a bright object on a dark background would evince a dim halo of light instead of pure blackness. That’s because the dimming isn’t local enough; there aren’t enough LEDs themselves to correspond with all 1920×1080 pixels of the TVs’ 1080p native resolution, so there’s some spillover along the edges. Samsung did not divulge exactly how many LEDs were used in its 46-inch model, and neither will Sony for its displays, but LG did. The 47LG90 has “1,536 individual light emitting-diodes arranged into 128 sectors,” according to the company. How much that number affects blooming is still an open question.
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.
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.
