A new entry level 4K Ultra HD LCD TV line LG Electronics dropped in the U.S. market two weeks ago has started to create a stir over how to define 4K UHD resolution.

LG’s new UF6800 LED LCD TV series, which includes 55- and 65-inch screen sizes, features a controversial new LCD panel that uses a white sub-pixel, along with the standard Red, Green and Blue (RGB) sub-pixels that make up each pixel, in order to produce a lower-cost 4K Ultra HD LCD TV.

Critics, who contacted HD Guru about the new sets, say the additional white sub-pixel reduces the number of RGB sub-pixels in the 3840 pixel count across the screen, and the set therefore fails to comply with the Consumer Electronics Association’s (CEA’s) terminology for 4K Ultra HD minimum performance attributes.

More on LG’s UF6800 RGBW LCD TV line after the jump:

LG acknowledges that by the CEA’s narrow 4K Ultra HD standards, the new panels do not comply with the terminology, and the company will not use the CEA’s voluntary 4K Ultra HDTV logo to promote or advertise the new sets.

But Tim Alessi, LG new product development director (pictured with a 55UF6800 at top), told HD Guru that doesn’t mean the TVs are not 4K UHD TVs by performance criteria used by most display standards groups in the world, including such organizations as the ISO, IDM, THX, and VESA.

“The Information Display Measurement standard says resolution should be measured by luminance, meaning the total number for black and white lines that distinguishes by contrast. It says each white line has to be three times brighter than the black line.

“Based on that definition of resolution, this panel clearly meets that, because it can easily pass the 3840×2160 and we’ve had that certified by different organizations around the world – InterTech in the U.K., TUV in Germany, and a number of different industry associations in China and Japan. We’ve got certification based on international standards saying that this meets the resolution of 4K,” he said.

Alessi called CEA’s certification, “a non-issue. We are positioning it as a 4K TV, based on international standards and certification. Resolution is really measured by luminance and not by chrominance.”

“There was something added to the CEA 4K Ultra HDTV terminology very late in the game that talked about every pixel being able to deliver the full range of color,” he said. “So, by that definition, we are not using the CEA 4K UHD logo.”

Under the CEA’s voluntary criteria for logo certification, a 4K UHD TV would have to have a total of 11,520 red, green and blue sub-pixels (three per 3840 pixels) in each of the 2,160 horizontal lines of resolution.

Instead, LG’s RGBW technology substitutes a white sub-pixel for every fourth sub-pixel across the screen. Each pixel is then comprised of four pixels, and the fourth sub-pixel is shared with the next adjacent pixel.

“There are still 3840 addressable sub-pixels of four across the screen,” Alessi explained. “Because color is a combination of both color and brightness – you can’t see color without any brightness – the real measurement of resolution is the contrast modulation looking about the number of addressable lines that can be changed from black to white at a certain brightness level.”

Alessi reminded that LG announced RGBW technology about a year and half ago at 2014 International CES. Since then, TVs using the technology have been sold in markets outside of the United States.

He said LG decided after the 2015 CES to bring it here as its new entry 4K UHD LED TV line, replacing the previously announced UF6700 series. That line was scrapped because it omitted built-in smart TV functionality, which would have limited its options to play streaming 4K content, he added.

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The UF6800 series allows LG to hit competitive price points and still include popular features like built-in 4K UHD streaming via the webOS platform, he said. The 65-inch 65UF6800 carries a $2,499 suggested retail price and is currently available on promotion at a $1,899. The 55-inch 55UF6800 carries a $1,699 suggested retail price and is being promoted by some retailers at $999.

Alessi said RGBW isn’t intended just for entry level models. Depending on how it is implemented, the RGBW technology will give LG a range of options in developing step-up sets as well. For example, Alessi said RGBW can be used for a 37 percent energy consumption savings in one implementation – and the UF6800 series models will both conform to the new EnergyStar 7 requirements coming this fall – or using a different implementation, it can be used to generate a 50 percent boost in brightness.

“We think it is a great technology, because as the market expands, we have options to provide either higher brightness or energy savings. That’s important since EnergyStar continues to evolve with tougher and tougher standards to meet. Quite frankly, the technology also offers us the ability to hit lower price points to make [4K UHD] more accessible for consumers.”

Alessi acknowledged that the technology’s weakness is its ability to display “pure color,” which shows up in single color test patterns. But he added that color saturation and color space tests conducted at LG’s lab in Lincolnshire, IL, show gamut and saturation are almost identical with RGB LED TVs under most conditions.

“There is no sacrifice in color reproduction,” he said.

“LG Display data shows that when analyzing different types of content the average color levels under most luminance conditions are for the most part identical, except in the area between 70 and 100 percent pure color,” said Alessi. “But in areas where you have more brightness, that’s where the RGBW excels. Under most conditions, their performance is roughly the same. When they looked at regular movies, TV dramas or sports programming, less than 5 percent of content fell in the 75 percent to  100 percent pure color area. So, we are talking about a very small area that I am going to say, is not noticeable by the average consumer.”

Alessi said that before bringing the TVs to the U.S., LG conducted consumer demonstration studies that compared LG’s reference model UF7600 TV, which sits right above the UF6800 series models in the lineup, alongside a UF6800 set and ran two brightness level tests.

“We got an interesting result. When the 7600 was set at 400 nits compared to the 6800 at the equivalent of 260 nits, the overall result was about equal — 73 percent said they were very satisfied with RGBW compared to 78 percent for the RGB model at a $300 premium, even at a lower brightness level.

“When the RGB model was equalized for brightness, the effect of the white sub-pixels really came through. People responded to the higher brightness. So even though the spec was the same the perceived brightness was higher, and the interesting thing was it was almost 2-to-1 preferred over the RGB. About 70 percent of people said they saw no difference. From a practical viewing standpoint, it is almost indiscernible.”

In a brief side-by-side demo given to HD Guru, we also found it hard to see a difference between the two models. Alessi said both series used In-Plane Switching (IPS) LED panels, which improves off-angle contrast and color performance compared with other LCD panels.

Despite the controversial nature of the technology, Alessi said LG has no current plans to call out the RGBW technology on the box or in product literature, adding that LG doesn’t spell out many of the technologies it employs in its products. He added that because the TVs meet international standards for 4K Ultra HD resolution, the consumer has no reason for concern.

By Greg Tarr


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