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How LG uses fuzzy math to label some of its LCD TVs as 4K

Jon L. Jacobi | Sept. 22, 2016
By replacing every fourth red, green, or blue subpixel with a white one, LG boosts the brightness of its 6100-, 6500-, and 6800-series models. The trick works, but it sacrifices resolution.

Even in an industry that rounds up 3840 pixels to 4000 pixels to market TVs as “4K,” it’s alarming that a major tech manufacturer would blur that definition even further. That manufacturer is LG Electronics, and the TVs in question are LG’s 6100-, 6500-, and 6800-series LCD models, which rolled out this year and last. These aren’t to be confused with LG’s OLED TVs, which remain among the best you can buy.

As with any other 4K TV, the panels in these LCD models have 2160 horizontal scan lines with 3840 pixels in each line. The pixels in these LG models, however, are very different from what you’ll find in competing 4K TVs—and that difference has a negative impact on image quality. It’s an issue that flies beneath most consumers' radar because LG doesn’t disclose its departure from conventional standards in its advertising or published specifications.

I’ve spoken with big-box store sales personnel about LG’s unorthodox technology, and they weren’t aware of it either.

These LG TVs aren’t bad, by most measures. And if you buy one, you might not notice their shortcomings for a while, if only because there’s so little 4K content available. But as that 4K content proliferates and you see it on 4K TVs that have more conventional pixels, you’re liable to be disappointed with your purchase.

LG’s fuzzy math

A single pixel in a conventional LCD display consists of three subpixels: red, green, and blue. A white subpixel can be added to that array to increase a panel’s brightness—it’s an inexpensive way to increase a panel’s luminance, although it also affects color saturation and gamut. Still, luminance is almost as important as the number of pixels for creating a crisp, detailed image. But a bright panel in and of itself won’t deliver the best-quality picture. 

LG takes an unorthodox approach to how it handles the white subpixels in its 6100-, 6500-, and 6800-series TVs. Instead of adding white subpixels to the RGB subpixel arrays, as it does with its OLED models, it replaces every fourth red, green, or blue subpixel with a white one. So three out of every four whole pixels are missing colors. The patterns below will give you a clearer idea of what I’m talking about.  

The RGB pixels in a normal LCD TV

rgb

In the standard RGB pixel arrangement, three subpixels (one red, one green, and one blue) make up one whole pixel: That’s 11,520 subpixels and 3840 whole pixels in each row.

The RGBW pixels in LG’s 6100-, 6500-, and 6800-series LCD TVs

rgbw c

 

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