Are dual-LCDs double the fun? New TV tech aims to find out

If one LCD is good, two is better, right? I'm not talking about two TVs in one room, though that's cool too. In the ongoing effort to improve picture quality of LCDs, companies like Hisense and Panasonic are working on dual-LCD, or what could probably be more accurately called dual-layer LCD. No, that's still not quite right. LCDs have lots of layers. How about Double Stuf LCD? Nailed it.

Double Stuf LCDs have the potential to improve the contrast ratio of a display with minimal additional power draw and without needing additional LEDs, like mini-LED.

Here's how the tech works, and my best guess as to whether it could be a player in the TV space.

Of LCDs and LEDs

LCDs work by managing light, light created by a group of light emitting diodes (LEDs) either along the edges of the screen or behind it. A layer of liquid crystal acts like a traffic cop to regulate this light by changing the polarity so another layer, a polarized filter, blocks it. If the liquid crystal pixels twist, the pixel is dark. If the liquid crystal doesn't twist, the layer is essentially "clear" and that pixel appears bright. Additional filters create color, diffuse the light and even add stuff like quantum dots, but for now we'll skip those.

The simple version: LEDs create light, the liquid crystal layer "blocks" it to create an image.

The problem, and what has always been LCD's problem, is this method doesn't block all the light. There's no such thing as a "black" LCD pixel. Some light always leaks through, which is why LCDs have always had worse black levels and contrast compared to other technologies, like OLED and (RIP), plasma.

Local dimming was and is a way to improve this. By dimming specific LEDs, or more accurately groups of LEDs called "zones," there's less light that has to be blocked, so the area on screen appears much darker, perhaps even black. For more on how this works, check out LED local dimming explained.

Ideally, there'd be one LED for every pixel, but that doesn't make financial, or technological sense. After all, if you could make 8 million LEDs that close together, why not just ditch the LC layer altogether? (Incidentally, this is what MicroLED does).

Most TVs have dozens of LEDs, either on the edges of the screen, or behind it. Fewer LEDs is cheaper and more energy efficient, but don't always look as good. More LEDs usually looks better, but costs more. If you add WAY more LEDs, you've got mini-LED.

If only there was a way to make the liquid crystal layer work better. Or, baring that, adding more liquid crystals or something. Well, that's what the Hisense ULED XD and Panasonic MegaCon promise: A way to improve how well the TV manipulates the light, after it's created by the LEDs.

Twinsies

Dual-LCD adds a second LC layer, essentially like having two TVs sharing one backlight. Another slice of meat in the LCD TV sandwich, as CNET's David Katzmaier wrote in his dual-LCD preview. This new second LC layer does the heavy lifting of predimming the light, where necessary. Hisense calls the new layer the "luminance" module and the other the "color" module.

In Hisense's prototypes and the current version of this TV (currently only available in China), the second layer was 1080p on a 4K display. Hisense promises that when this tech reaches US shores, both layers will be 4K. This means that essentially it's an LCD TV with a 8 million zone backlight, far more than even mini-LED has. With two 4K modules, each pixel gets a far greater ability to block the light from the backlight, greatly improving this longstanding LCD issue and improving the contrast ratio.

To further aid the overall contrast ratio, there's still a locally dimming backlight. In the current model it has 132 zones, which on its own would be reasonable for a traditional TV. 

Together Hisense claims a native 1,000,000:1 contrast ratio, though as we've discussed, these numbers are increasingly meaningless with today's televisions. The claim of a black level of 0.00003 nits is better than we've ever measured on an LCD, but still higher than OLED's 0 nits. The claim of 1,000 nits peak brightness is higher than OLED, however.

Potential downsides? Off-axis performance, or how it looks when you're not sitting directly in front. David saw some brightness fall off on the model he saw in May. I saw a presumably different example at the IFA show in Berlin in September and didn't see as pronounced an issue. However, my viewing was on the floor of a trade show, so we'll have to wait until we see some actual production models.

Price-wise, Hisense is aiming to be cheaper than OLED, though probably similar-to or more than higher-end LCDs. For reference the HZ65U9E, its 65-inch model for sale in China now, is 17,999 yuan, which converts to about $2,500, £2,000, or AU$3,700.

Panasonic is the only other company that has announced it's working on dual-LCD. Its prototype, which it's calling MegaCon, aka Mega Contrast, also has a claimed 1,000 nits brightness and 1,000,000:1 contrast ratio. It's also claiming it can produce 99% of DCI-P3 color space, wider than what wide color gamut TVs can create now, though 1% less than what Hisense claims for its ULED XD. Interestingly, Panasonic makes a point to say that its TV doesn't have any off-axis viewing issues, perhaps because it's using IPS panels while Hisense is using VA.

There's no price or other info, but given its chunky looks it's either very early in the prototype stage, or more likely, aimed for post-production and broadcast TV markets. It's worth noting that Panasonic no longer sells TVs in the US.

OLED is the elephant in the room, of course, and dual-LCD is going to have to offer a compelling reason for people to consider it over the current picture quality king, or the presumably lower prices of regular LCD. On the picture quality front, that low black level is paired with a claimed better-than-OLED light output. OLEDs aren't dim by any stretch, but they're dimmer than most HDR-capable LCDs. Brighter HDR peaks, or potentially better performance in bright rooms, could be a major selling point.

Double your fun, it's the right one

Manufacturers have a lot of money in LCD, and that's not changing any time soon. They're always looking out for the next big thing, which is how we got OLED and how we'll be getting MicroLED. Before we get to the next gen, there's still a lot of improvement to be made with the current gen. Mini-LED is one aspect of that, and potentially so is dual-LCD. No doubt we'll hear more about both at CES in January.

Got a question for Geoff? First, check out all the other articles he's written on topics like why you shouldn't buy expensive HDMI cables, TV resolutions explained, how HDR works and more.

Still have a question? Tweet at him @TechWriterGeoff, then check out his travel photography on Instagram. He also thinks you should check out his best-selling sci-fi novel and its sequel.