This is the beginning of what I hope will be a long-running conversation between you and me. I will write about the things that I consider important, but if you think something else is more important or just more interesting let me know. eMail me with any questions you might have and I will make my best effort to address those issues.
The audio/video/multimedia industry is fraught with myths. Most of these are started by competing firms or technologies and are often misleading to many of us. I thought I would occasionally talk about some of this folklore, so I'll start today. Hopefully this will shed a little light on some misunderstood subjects. So let's get to it.
By far, the gatherer of the most legends is Plasma TV or Plasma Display Technology. This often outstanding viewing medium is the target of so much confusion, it's scary. Let's talk about some of these:
- Plasma TVs lose their gas. They have to be recharged every couple of years.
- Similar to other fixed pixel displays, plasma TVs have thousands of tiny locations, where red, green, and blue are mixed to form all the colors in our movies. Each of these pixels(picture elements) contains a tiny amount of gas. When an electric current passes through that gas, it gets so hot that the gas molecules fly apart and form a plasma. The electrons floating around in that plasma strike a phosphor on the front of the screen causing it to glow. We see light. All of these little lights form shapes on the screen and we get a picture.
- The gas doesn't escape. It is permanently sealed in. It can't leak unless the screen is broken in which case can kiss your lovely expensive TV goodbye. Repairing a broken screen is essentially replacing the plasma TV. Get it insured.
- Plasmas always burn. They can get a permanent image and you have to throw them away.
- First let me say that any display technology can retain an image. However, this is far more likely in a phosphor-based display (e.g. plasma, picture tube…) than in any solid-state technology (LCD, DLP, DiLA…). Admittedly, burn is most likely in plasmas because they use a high-persistence phosphor. But…
- Early in its life any plasma will retain images. You can see them when the set is turning on or off. However, once the phosphor ages a little this effect disappears.
Burning is different from early-life image retention. Plasmas fail because the phosphor fades as it is used. If one part of the phosphor is used much more than the rest of the screen, it will fade faster and you will be able to see the border of that area whenever you watch the picture, especially in dark scenes. This rarely occurs but it can, for instance, if you watch CNN all day. The crawl at the bottom will eventually burn (fade) into the screen and you will see a line across the bottom of the screen if you ever watch anything else. If your plasma does burn, use your manufacturer's burn eraser (on the user menu) or lacking that, leave "snow" on your screen overnight. This should help. Video games, at one time the worst culprits, and most of the plasma displays themselves have anti-burn technology so this occurs infrequently.
- Plasmas get dim. They don't last long.
- Plasmas do fade. Almost all technologies fade. But for plasmas, picture tube TVs, and RPTVs, this is the normal way they fail. So let's see how long a plasma should last.
- Conservatively, the half-life of a plasma screen is 20,000 hours. This means If you watch TV 4 hours a day 365 days a year your plasma will reach ½ brightness in 13.7 years.If ½ brightness is still useful to you then your plasma is still operational. If this is too dim for your application, then you only got 13 years out of your set. Some plasmas now have half-lives over 60,000 hours. Is 40 years enough? Very few conventional TVs, or even LCDs will last that long. Plasma may well be the longest-lasting technology. By the way, if you get your plasma properly calibrated, not only will your picture be vastly better, but your set will last longer.
- Plasma has no contrast. It's blacks are not black.
- I will not get into a long description of this before getting to the point. This is just wrong. A properly calibrated CRT (picture tube) based TV in your living room typically has a contrast ratio around 30:1. A movie theater is around 200:1 although the film itself is only around 100:1. I have calibrated plasma TVs and achieved a contrast ratio of almost 350:1. The white was 350 times brighter than the black. Better than a theater. Very few technologies can match that. Before you jump all over me about your plasma has a contrast ratio of 4000:1 see the next item.
- Plasmas can have contrast ratios of 4000:1.
- Manufacturers advertise contrast ratios, for many different technologies, that are all over the map. They range from 150:1 to 4000:1. How good can a contrast ratio be?
- First let me say that I don't know how these are measured by manufacturers, but ISF (Imaging Science Foundation) measures contrast ratio of a properly calibrated TV by displaying a checkerboard pattern and comparing the light output of a white block with a black block. This takes the measurement using an image that actually contains contrast. We do not measure a white screen and a black screen separately. The 350:1 ratio mentioned above was outstanding.
Second, let me say that the human eye, in color, can see a contrast ratio of only about 800:1. The difference between 1500:1 and 4000:1 may not mean much.
Get your set calibrated and enjoy the picture. It's all good.
- Plasma TVs can't be used where there is much light in the room.
- No TV looks like it should unless the room is dark. But plasma probably stands up to ambient light better than any other technology. It can be very bright.
- Plasma TVs cost less than $3000.00.
- Some cost less than $2000. They display a picture. So does an Etch-a Sketch.
- I have yet to see a cheap plasma that displays a decent picture let alone a High Definition (HD) picture. At best these are Enhanced Definition (ED) capable of displaying 480p (the definition of that some other time). That means that a typical 720 or 1080 line HD picture is down-converted to 480 horizontal lines. The HD Picture is no longer HD.
Most of the inexpensive sets are noisy. The pictures have a lot of fluctuation in dark areas and the gray is sloppy. Many cannot even be properly calibrated.
If you are going to buy a plasma display, buy a good one. Even a small 42" HD plasma will cost over $4,000. If you get it for less on the Internet, don't count on the manufacturer honoring the warrantee. It may very well be gray market/trans-shipped. You have to buy from an authorized dealer.
Note that a 42" plasma typically has a resolution of 1024x768. 720p requires 1280x720. Get a 50" if you can.
There are other myths about plasmas but I think we covered the major issues. Yes, plasma, like all technologies has its flaws, but it is a good reliable technology capable of presenting excellent pictures.
I hope all of you enjoyed this little dissertation. Please feel free to email me at info@infinitesightandsound.com with any questions or suggest any topic for discussion in this little forum.
More myths another time. Acoustics has gathered quite a few. What shall we talk about next?