Plasma TVs Explained

By March 5, 2003

At my age I can remember television when it first started. Back then it was a tiny, round screen that provided a somewhat wavy black and white picture. Often the TV was in the same wooden cabinet as a record player and a radio. The picture was a marvel of modern science and as a child I sat in front of that screen for hours. Now, the demands of the public are for ever greater clarity from the television screen. Near the apex of this quest, at least for the moment, is the plasma screen display. For home theater enthusiasts this is the Holy Grail, if they can afford it. The technology for the plasma screen affords a greater precision, range of color, contrast and viewing angle than most other types of sets on the market.

In the old fashion television set the picture is displayed by a cathode ray tube. This is a vacuum tube that shoots a stream of electrons, hitting a group of phosphors. There are three phosphors for each dot or pixel of the picture, red, green and blue. By controlling which phosphors are hit, the duration and strength of the hit the tube paints a picture that we can enjoy. The problem with this method of picture production is the cathode ray tube is heavy, large, especially in depth, and prone to break. Now, those geniuses who create new technology for a living have come up with something better, the plasma screen. Instead of a stream of electrons shot at the phosphors, a gas is excited into the highly charged plasma state and shot at the pixels. There are still three sub-pixels for each dot, the same red, green and blue, but since the plasma jet is easier to aim there can be far more pixels per inch resulting in greater resolution. With this system you can get over 16 million different colors. Most men can only name red, yellow, blue, green and other, but it’s nice to know they are there.

Since the days when the whole family sat directly in front of the TV set are long gone, the viewing angle is a very important consideration. Most people want to have friends over to show off their home theater so you want the picture visible from all parts of your living room. This means you not only want a large screen but you want the same quality of picture from anywhere in the room. With rear projection televisions the viewing angle is about 45 degrees. This means if you pick a spot on the screen you need to draw two lines, 45 degrees apart and you have to be within that area to properly see the picture. What this translates to in reality is only the people directly in front of the rear projection screen will see the picture. A few inches to either side will degrade the picture. With the plasma screen the viewing angle is a whopping 160 degrees. This basically covers the whole area in front of the screen. Unlike the old cathode ray sets the screen of the plasma set is flat. This not only adds to the viewing angle but it makes glare a thing of the past. Another factor is ambient room light. With a rear projection TV the room has to be fairly dark to enjoy the picture. The plasma set on the other hand maintains its quality even in relatively well lit rooms.

Now, a little more about the thickness of the plasma screen, the cathode ray tube requires a good amount of empty space to focus the electron beam that forms the picture. The gas that is excited to the plasma state is captured between two flat glass panels about 0.1mm apart. This permits a very small depth to the set. It is not uncommon for the entire depth of a plasma screen television to be about four inches. This means the set can be mounted on a wall, much like a picture. Now the set does have some weight to it. They are also expensive so pay the dealership a few extra dollars and have them professionally mount the set where you want it. There is nothing like the sound of thousands of your dollars crashing down into pieces on your living room floor. There are cables going to and from the set so it’s better to let the pros hide them for you.

Another reason why plasma is better is that the screen is not affected by magnetic fields. With the advent of home theater we now have speakers all over the room. While most speakers for home theater use are magnetically shielded an unshielded speaker will distort and harm a regular TV set. Most of have seen the colorful wavy lines when a speaker comes too close to the regular TV set’s screen.

The regular cathode ray tube set paints the picture in two passes. The odd lines are painted first followed by a second pass that paints the even lines. This results in picture flicker. The plasma screen on the other hand uses progressive scan. Thanks to advances in computer style memory the whole picture is assembled in memory and sent to the screen in one, fast shot. This provides a clear, flicker free picture. Since the screen is flat there is no distortion at the edges of the screen. Ever notice how old TVs get warm? This heat comes from all the energy the set requires. In contrast the plasma set requires a lot less power and will remain cool. This translates to more than a cooler set; it means less electricity is required and parts will last longer. A typical plasma set will last over ten years with little or no problems.

Of course, all of the features we have come to expect on a television screen are present with the plasma screen. There is picture in picture, the ability to use the screen with either your home theater or with the computer and other devices. The prices of plasma screens are dropping as more and more consumers demand them. Currently you are looking at $4,000 to $10,000 for a big screen model. Some manufacturers are now coming out with screens as small as 15″ that are small enough to bring from room to room. They also typically have at least two modes, the regular 4:3 aspect ratio of the customary TV and the enhanced 16:9 anamorphic aspect ratio used with DVDs and many digital cable and satellite sources. This has become very import to the home theater person lately. With digital home theater sources becoming available to more households than ever people want a television that will show every little detail of the picture.

So for compact size, clarity of picture and compatibility with all your video sources the plasma screen is the way to go, if you can afford it.

Editors' Recommendations