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HD 101: What is local dimming?

Ben Drawbaugh
One thing that makes covering LCD TVs so interesting is that the technology is always advancing and one innovation that might be the biggest in LCDs yet, is local dimming. But you're probably wondering, what is it exactly? Well in non-edgelit LED LCDs TV, there's an array of LED lights behind the liquid crystal pixels, and local dimming is when sections of the LED array are turned off or dimmed to help produce the deep blacks -- like Kuro deep. But while this tech can produce very deep blacks and fantastic contrast, there's a catch, it also create an artifact referred to as a halo around bright objects. Example: the two images above are of the opening scene of The Matrix (cops shining a flash light) it's pretty easy to tell which is the plasma and which is the LED LCD with local dimming. Of course we don't exactly watch movies with flash lights or star fields every night, so after the break are more pictures of a normal dark scene that also expose the artifact caused by local dimming (we have to point out that the camera makes it more drastic than it appears in reality). So while we wouldn't buy an LCD without local dimming, there's still a lot to look forward to in the next generation when the dimming is sure to become more local, and thus the artifact will be minimized. At the same time these advancements should help produce more detail in blacks, which is harder to notice at first, but just as annoying once you do.

Just getting into HD? Check out these other HD 101 features:
Overscan and why all TVs do it
What is ATSC, PSIP, QAM, and 8-VSB?
How to use Dolby TrueHD and DTS-HD with your PS3
Why there are black bars on HDTVs
IR blasters, HDMI-CEC, RS-232 and IP control

LED back-lit LCD with local dimming


LED backlit LCD