HDTV Trends For 2008

So, I'll admit it right up front -- I'm no consumer electronics expert. I love electronic toys, but other than that, I'm about as qualified to cover the consumer electronics show as you are. That said, I hit press conferences from LG and Toshiba this morning, and here's what I learned.I got to LG a bit late, so I didn't get its complete dog and pony show for TVs. On the nontechnical side, LG seems to be doing a great job of partnering to extend its technologies. At this conference, LG announced a partnership on the audio side with well known audiophile Mark Levinson. LG will develop products with Levinson that will carry his name. It also announced a partnership with Netflix, but was sketchy on exactly what would come out of that deal.

From both press conferences, you'll see a lot of TVs claiming LED/LCD technology. You'll also see many fewer sets with 720P resolution, 1080P is now where it's at. But back to LED/LCD. The LCD part is no different than it's ever been. In fact, you'll see that most manufacturers carry the same size panels across the board. That's in part because there are only a handful of panel manufacturers. The differences are really in the control systems, associated electronics, packaging, and backlighting technologies. This last is where LEDs come in. Most everyone is now familiar with white LEDs. These are quite a breakthrough, whether for high-efficiency flashlights or for almost any other application where a pure white light is needed. Unlike incandescents, white LEDs give off very little heat, which is what makes them energy efficient.

Before I explain how they're used in LCD HDTVs, a word about the backlighting problem. As LCD panels are used in laptops, the light behind the LCD panel is a constant brightness. The liquid crystals in the LCD display act as shutters, letting varying amounts of red, green, and blue light through. The crystals are opaque, but they can't completely shut out all light, and they're usually controlled by an eight-bit control system, which means that you'll get 256 shades of red, green, and blue, which combine to make hundreds of thousands of shades of color. But because we're combining red, green, and blue, the hardest thing to get right is perfectly combining the colors to get even shades of gray.

You'll hear a lot about contrast ratios, which are today usually in the thousands (the ratio between the darkest black and the brightest white.) That's pretty darn good, but you'll still rarely see a true black on an LCD TV -- and that tends to bug us. The solution has been to vary the brightness of the backlight. So if you have a very dark scene, just turn down the backlighting and you can get much closer to true black. That's great, unless you're looking at, say, the sun rising over a mountain. The base of the mountain will be almost pure black, or at least it should be, and the sun should be pure white. LCDs aren't good at this, and that's one of the reasons that HD snobs still prefer plasmas (even though they have their own problems, like burn in and a comparatively short life span).

Here's where the white LEDs come in. Vendors use these LEDs to produce the backlighting and can vary the brightness locally. In the case of Toshiba, it uses 1,152 LEDs in 96 zones. So, in the scene described above, the zones near the sun would have backlighting on full blast while the zones at the base of the mountain would be practically off. The result is contrast ratios in the hundreds of thousands, or about 100 times better than older technology.

Last year you got localized dynamic backlighting in the very high end sets; now it's more universally available. The other thing you'll see is a move to 14-bit gradations. That means more than 16,000 shades of red, green, and blue, and therefore less noticeable transitions in color.

While this technology sounds cool, I'm not sure sure this is the year to buy it. In current LCDs, the most annoying problem tends to be "banding," where you can essentially see differences in backlighting that appear as bands on the screen. Far away, it's not terribly noticeable (like when you're in the back of the room at a press conference), but up close, these bands are extremely noticeable and very annoying. I was hoping that the local dynamic backlighting would eliminate this problem, but when I went up and took a good look at the LGs on display, I was disappointed to see some pretty nasty banding. It may be that for the conference LG had the brightness turned all the way up, and that resulted in worse banding, but I'd still be very careful in buying one of these sets.

The final improvement for this year -- at least the only other one I took notes on -- had to do with refresh rate and some special modes to support gaming. Most of last year's HDTVs refreshed the screen at 60 Hz, that's plenty fast for supporting continuous motion, but that motion will often look blurry, and the colors maybe duller than they should be. Higher-end sets will now support 120-Hz refresh rates, which significantly help the problem.

For gamers, there's a slightly different problem. The control systems of a typical HDTV introduce some latency in rendering the screen That is to say, it takes a while for the TV to do its thing, so the image you see probably got to the TV a good 100 milliseconds or so before you see it. For broadcast television, this isn't a problem, but for gaming, some people claim they can detect, and are annoyed by, this delay. The solution is get the control circuitry out of the way and to simply present the images just as they were delivered from the game box. Toshiba says that doing this eliminates about 42 milliseconds of latency.

To learn more about the ins and out of HDTVs, see Alex Wolfe's excellent primer.