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Television: acronyms, specifications, and geometry.

IF A NEW high-tech television is in your future, you might want to bone up on your geometry. Let me explain. In the early days of television, the National Television Standards Commission (NTSC) set the aspect ratio (width divided by height) of the television screen at 4 by 3 or 1.33. Today, you can still buy 4-by-3 sets, or you can buy a widescreen set with an aspect ratio of 16 by 9 or 1.78. Most television stations or channels still broadcast in a 4-by-3 format, so a television set with that aspect ratio makes sense.

However, if you watch a lot of movies or programs on high-definition, cable, or satellite channels, a number of these will be widescreen productions. Now here is the downside of this geometry. If you watch a 16-by-9 program on a 4-by-3 set, the screen is "letter boxed"--meaning it has black bars on the top and bottom of the screen (Figure 1, top). If you watch a 4-by-3 program on a 16-by-9 set, the image is "pillar boxed"--meaning there are black bars on the left and right of the screen (Figure 1, bottom). In either case, a sizable portion of the television screen is unused. (I should mention here that Europe and other parts of the world do not use the NTSC standard, so some of what follows does not apply to readers outside the U.S.)

[FIGURE 1 OMITTED]

There are several "work arounds" for letter boxing and pillar boxing. Most widescreen sets (16 by 9) have aspect adjustments. The most common aspect adjustment is to stretch--or widen--a 4-by-3 program to fill the widescreen. I suppose you could get used to this, but it sure makes people look plump. Going in the opposite direction, some widescreen DVD movies are also available in "full-screen" versions, but this is becoming less and less common.

A second downside to this geometry quandary is that watching a 4-by-3 program on a large widescreen set (unstretched) is like watching it on a significantly smaller 4-by-3 set. What you thought was going to look like a large picture looks a lot smaller. Here's a brief tabular presentation of effective viewing reduction for widescreen sets of various sizes. (The figures are for diagonal measurements and are in inches.)

CNet has an online calculator that will give you these comparisons for any size widescreen set at http://reviews.cnet.com/ 4520-7608_7-1016109-4.html. Hint: CNet calls pillar boxing "window boxing," and remember to use the lower of the two calculators.

The bottom line is you must examine your viewing habits before you buy a new television. Of course, if you have the space, you can have a television room and a separate home theater room for your widescreen. Ultimately, most people will buy a newer widescreen set because they want to move up to High-Definition Television (HDTV) and because they like the movie theater look of the newer format.

The old television standard set by the NTSC was labeled 480i. This format had 480 horizontal lines of resolution that were, as the "i" signifies, "interlaced." That is, the television displayed the odd-numbered lines every 60th of a second and the even-numbered lines in the next 60th of a second. You can actually see these lines if you look closely at the screen. Unfortunately, viewers rarely saw a television program with all 480 lines of resolution, since most programming was produced with only about 250 lines of resolution. And interlacing causes an imperceptible flicker that can contribute to eyestrain.

The most common HDTV standards are 720p and 1080i or 1080p. Each has as many lines of resolution as the numbers suggest. The "p" stands for "progressive scan," which means that all lines are displayed at one time--not interlaced. Suffice it to say, if you buy an HDTV you should be sure it can display at least one of the standards mentioned here. Another important consideration is the number of pixels (picture elements) an HDTV can display. Most newer HDTVs have pixel ratings of about 1280 by 720. Some higher-end units have specs such as 1920 by 1080. I doubt that most viewers would notice much difference. Both 720p and 1080i or 1080p are radical improvements over the older standard. You will notice a striking difference.

Once you have an HDTV, you need a source for HD programming. If you live in a large metropolitan area, it is possible to receive broadcast HD programming using a special antenna. However, an antenna is not a very good option, so most people get their HD programming via cable or satellite dish. Although it varies by provider, the cost of upgrading your service is likely to be an additional $5 to $10 a month for rental of an HD cable box. The number of HD channels you receive will also vary by location and provider. Most providers bundle their channels so the programming you receive may also relate to which premium package( s) you subscribe to.

Whichever method of delivery you choose, you will probably be able to receive several dozen HD channels. In my area, for example, there are about 20 HD cable channels, including all the major networks and several local stations. Networks tend to produce HD programming for prime time shows but not for morning and afternoon shows. Incidentally, I would recommend that you get your cable or satellite provider to install your HD receiver rather trying to do it yourself.

Here are a few suggestions for purchasing an HDTV. First, the size of the TV you need is related to how far from the screen you plan to sit. I suggest you pace off this distance in your home and then stand that far away from any TV you are considering buying. Larger rooms need larger TVs.

Second, viewing angle may be important. With some HDTVs, you have to sit close to the center of the screen to see it clearly. You can easily check this out in the store by moving from side to side. Or you could look it up in the technical documentation for the TV. Incidentally, viewing angle is not just a side-to-side issue, it is also an up-and-down issue. I have a friend with a projection HDTV that is impossible to see if you are standing--you have to be sitting to see it.

Third, when you go to the store, note the lighting level in the showroom. Showrooms are often quite dark, which makes the TV projections look brighter. Of course, you can always ask for the brightness ratings of various sets.

Fourth, the proof is in the watching, but the problem is, watching what? You can always take your favorite DVD with you to the store, but DVDs do not have high-definition video. Ask the salesperson to show the same HD program on the sets you like the best and are considering purchasing.

If you are a movie buff, sound may be almost as important as picture quality. Regular television has stereo sound--two audio channels. HDTV has digital surround sound--five audio channels: left and right front, left and right rear, and a center channel for dialogue. You may also want a "subwoofer" for impressive bass sound. Most HDTVs simulate surround-sound on their small internal speakers, which is not very impressive. So if sound is your concern, you need a real surround-sound system. Again, there is a glitch. If you purchase an LCD or plasma thin-screen HDTV and hang it on the wall, where are you going to put the surround-sound audio system? You either have to buy a wall-mounted audio system or put a cabinet or rack under your flat-screen TV. I am still arguing with myself about how I am going to handle this issue in my own family room.

Now for the tough decision. There are five major types of HDTVs: tube, rear projection, LCD, plasma, and front projection. Which technology to choose? Here are a few of the major attributes of each. It's tough to beat a good old tube-type TV, except that they are heavy and bulky. Tube sets work best in small intimate rooms, where large screen size is unnecessary. Rear projection sets usually use either DLP (digital light processing) or LCD (liquid crystal display) projectors inside a relatively large box. If you don't mind the bulk, 50-inch or larger rear-projection HDTVs are some of the best buys. Do check out the viewing angle as discussed above, since some rear projectors don't do well on this specification.

LCD HDTVs have many advantages. They are lightweight, thin, bright, durable, and easy to mount on a wall. The only limitation is screen size. Today, a 40-inch LCD set is the largest model commonly available. Although a few manufacturers make 46-inch sets, they are expensive. The very best available flat-panel TV is a 46-inch LCD with 1080p and about 1920 by 1080 pixels.

Plasma HDTVs are heavy and run hotter than most other types of TVs. Plasma sets are almost as thin as LCD TVs and are commonly available in larger screen sizes. Plasma sets can suffer "burn-in," which permanently damages the screen if a still image or logo stays on the screen too long. Watching CNN Headline News or a stock ticker for long periods might cause burn-in. Some newer plasma sets have special circuitry that helps prevent the problem, but caution is still urged in the first 100 hours of use. Front projectors are usually used in home theaters, so I won't go into them in this column.

Given all of the above, I am holding out for a large-screen LCD TV, but I want a 46- to 50-inch set. Whatever kind of television you have, happy viewing.
Widescreen   Size 4-by-3 Size
   50               41
   42               34
   36               29


ROYAL VAN HORN is a professor of education at the University of North Florida, Jacksonville (e-mail: rvanhorn@unf.edu; websites: www.electronicscholar.com and www.luckychild.us).
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Title Annotation:TECHNOLOGY
Author:Van Horn, Royal
Publication:Phi Delta Kappan
Geographic Code:1USA
Date:Apr 1, 2006
Words:1656
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