One of the features of the new high-end LCD HDTVs is the ability to control individual LED lights on an edge-lit display. This technology has been branded by various manufacturers with names like “Micro Dimming” and “Pixel Orbiter.” While these differentiating factors may seem trivial, there are important differences in how each manufacturer implements its local dimming solution. Here we will explain the basics of LED local dimming and compare how each manufacturer implements it in their TVs.
This illustration from a Samsung QLED presentation compares the classic edge-lit array (left) to a version with individual dimmable zones (right).
The basic idea behind LED Local Dimming is simple: instead of illuminating the entire backlight at once like most LCD TVs, an LED Local Dimming TV turns off certain LEDs when needed to control the intensity of specific areas on the screen. The result is improved black levels in scenes where there are both bright objects and dark regions—a challenging task for any type of LCD.
LEDs in action
The most common implementation of LED edge lighting is to simply turn off the LEDs in “problem” areas after each LCD refresh. However, this method is not without its challenges: the dimming algorithm must be accurate enough that an object’s true color and location can’t be easily detected when it changes from bright to dark and back again.
Another approach is to dim only parts of an LED array, for example turning off every other row or column. This solution does a better job of maintaining the image’s integrity but requires very accurate control over which LEDs should be lit and when.
Finally, some manufacturers have added a layer of complexity by grouping specific LEDs together into larger clusters that can be turned off or on as needed. This solution provides good lighting control but makes the TV more expensive to manufacture.
For example, a QLED Series 8 8K TV might have four “quadrants” of LEDs that are individually dimmable for finer control over specific areas of the screen. Meanwhile, an entry-level 4K UHD HDR 600 TV might simply dim or turn off all of its LEDs after each refresh cycle.
LED lighting technology is still in its relative infancy, so the quality of local dimming can vary significantly even within the same brand. To help you better understand how each manufacturer implements LED Local Dimming on their TVs, we’ve put together this infographic which compares their various approaches