HDTV Tech

Buying a new TV ain't what it used to be—there are a lot more choices and features to think about than yesteryear, when the only decision you needed to make was screen size. Among the most common questions I'm asked these days is, "Should I get an LCD or plasma flat-panel TV?" If you want the quick answer, jump to the end of this article. But if you want to understand the answer, read on.

When we wrote this feature for last year’s HDTV Buyer’s Guide issue, the flat-panel HDTV market was much simpler. 3D was nowhere in sight, and much of our analysis boiled down to the pros and cons of LCD and plasma technology. This year, 3D is just one of the newer wrinkles in the market. The number of plasmas in the market isn’t what it was just a few years ago, but plasma is not only hanging on, the best plasmas still stake a legitimate claim to being the best flat panels available. With LCDs, manufacturers are aggressively using the backlighting techniques to market the sets. In fact, LCDs are getting more and more sophisticated and offering serious potential value. There’s a lot to learn, so let’s get going.

By now, most home theater fans have undoubtedly grown used to seeing letterbox bars on many movies they watch. In today’s high-definition era, any content with an aspect ratio that’s greater than a 16:9 (a.k.a. 1.78:1) HDTV screen must be presented with black bars on the top and bottom of the frame. Blu-ray viewers have many examples of this. Approximately half of all modern theatrical films are photographed in the scope aspect ratio of 2.40:1. Iron Man, Tropic Thunder, and Wall-E fall into that category. Scope photography is sometimes referred to as 2.35:1 for reasons that are too complicated to explain in detail here. Just know that 2.40:1 is technically correct, although many people in the industry continue to use the term 2.35:1 interchangeably. At the other extreme, material narrower than 16:9 (classics like Casablanca and The Adventures of Robin Hood are 1.37:1) will have pillarbox bars on the sides. In the middle, movies composed for 1.85:1 (such as the The Sixth Sense, Hellboy, or Knocked Up) nearly fill an HDTV.

In the November 2007 issue, I tested 74 HDTVs for their ability to process 1080i signals, the highest resolution standard found on most of the broadcast and cable networks. A number of the remaining HDTVs to be introduced in 2007 arrived too late for our November issue. We decided to follow up with some more displays. Due to space constraints, this article will refer to previous articles more than we normally do. On the bright side, all the articles mentioned (including the November 2007 test) are available on this site.

The coolest demo I saw at CEDIA 2007 was a demo I saw at CEDIA 2006. The original demo was at the Planar suite. Dolby now owns the company that was working with Planar, BrightSide Technologies, and the technology shown in these demos has a name—Dolby Vision. The short version is this: Using LEDs, you can dim specific areas of the backlight to go along with what is happening with the video. In other words, you can dim certain areas of the screen, while keeping other areas bright. In the simplest form, picture a split screen with black on one side and white on the other. Local dimming would allow the LEDs on the black side to be off and the LEDs on the white side to be lit. The result is a fantastic, legitimate contrast ratio, along with possible energy savings and a host of other potential benefits. But first, we have to understand the problem before we can talk about this solution.