SERIOUS ISSUES WITH PLASMA HDTV
by Greg Gibson

In our last tutorial on HDTV, we want to provide you with some information received from the various manufacturers’ technical representatives at the 2004 Consumer Electronics Show (CES). We spent considerable time talking to the reps, because we have received numerous complaints from readers about their HDTVs and we wanted to do our homework/research before we wrote this article.

But first, let me share a typical email I have received:

“… My wife and I have noticed that our Plasma [HDTV] is not as bright or the colors as vibrant as when we first bought the set. I have tried to increase the brightness and contrast, but nothing seems to work. The set is only 2 years old. What is wrong?”

In our previous articles and Q&As, we have provided a solid primer about the four basic HDTV technologies: (1) direct view and projection tube sets [big, bulky, heavy, good picture]; (2) plasma flat panel sets [sleek, thin, light, brilliant colors, most expensive]; (3) Liquid crystal display (LCD) flat panel sets [thin, good colors, more expensive]; and the newest (4) Digital light processors (DLP) projection sets [thinner and more expensive than tube sets].

In that article, we noted the increasing costs for each technology, and the obvious advantages and disadvantages for each technology.

In this article, we want to provide insights that we have received from technical sources (Manufacturer’s reps, HDTV repairmen, HDTV warrantee services]. In particular, we want to focus on Plasma TVs – because the cost of plasma HDTV can reach $10,000 we felt it prudent to provide readers with important information so a fully knowledgeable decision can be made.

Please note that we do not have specific, detailed technical data on HDTV performance reliability – apparently, detailed information is either unavailable or considered confidential… in any event, it is not published. Therefore, you will have to take this information on face value, and consider the context it was provided to us.

Tube Sets

Both the direct view single picture tube HDTVs and the 3-tube projection HDTVs, utilize technology that has been around since the 1950s. These sets, while bulky and heavy, are generally very reliable. Feedback we have received from numerous TV Repairmen is that these sets usually don’t have many problems, and if they do the problems will occur within the first year. Then there is a period of several years where the set functions well, with an average useful life expectancy of 7 years or more (depending on amount of viewing time). When problems are encountered later in life, they typically involve aging issues with capacitors, the picture tubes, power supply, etc. In summary, tube sets offer the highest reliability, and excellent cost and picture quality of the HDTV technologies.

Plasma Flat Screens

Plasma sets are initially brilliant, vibrant colors and have excellent contrast ratios. However, Industry experience (as reported to us at CES2004) has been to classify Plasma sets as having a “halflife” of about 10,000 to 20,000 hours. That means that in this period, the brightness of the set will degrade to half of the initial value. This phenomena results in a picture that is “washed out” or “tired” looking. This can be exacerbated by the setting utilized by the viewer in setting the maximum brightness, contrast, and color… “showroom floor” settings are on maximum to give the consumer a “wow” factor – but manufacturers recommend that the owner reduce these settings so as to provide a softer picture which slows the picture degradation.

If your viewing is to turn on your set and leave it on 10 hours a day, in about 3 years you will reach the 10,000 hour level. Also, this “half-life” is not a sudden degradation – you might start noticing a gradually reduced picture quality well prior to this arbitrary point.

This phenomena is typical of plasma sets. Obviously, manufacturers know this, and are developing manufacturing techniques that promise to provide increased longevity with decreased degradation. Therefore, care must be exercised when purchasing a plasma. While plasma has an excellent picture (current pick of the litter), the current high prices make plasmas the most expensive of the technologies – so if price is a serious consideration, the consumer might want to consider how they would feel if they become dissatisfied with the picture (and need to buy a new set) in a little as 4 or 5 years.

In addition, as you have read in our other articles – true HDTV is 1080i. Plasma TVs provide a picture down-converted to 720p. 1080p plasma televisions are due to be launched in 2005 to 2006. Fortunately, 720p is a very high resolution but as a consumer, you should know it involves a down-converter.

LCD Flat Screen

LCDs offer significantly improved picture stability over plasma sets. While an LCD will also “tire” over time, the “halflife” for an LCD set is generally expected at 30,000 to 40,000 hours. This increased period would make the LCD set effective lifetime 2 to 3 times longer than a comparable plasma.

However, an LCD picture is composed of small pixels (red, green, blue) that cycle on/off to create the picture. Since the LCD pixel is actually turning on/off, there is an issue with the refresh rate – the ability for the picture to display fast moving images across the screen. Early LCD models suffered with long refresh rates, but current new models have an acceptably faster rate.

Since the LCD pixels turn on/off, some pixels can fail over time. If there are a million pixels, a failure rate of 1 in a million would equate to one failed pixel. If the pixel fails in the off condition, the eye will likely not be able to differentiate the difference. However, if the pixel fails in the on condition, the eye can differentiate the error – and perceive the failed pixel. If the pixel is red, the situation is exacerbated – and the eye will immediately lock onto the pixel every time. Sort of how you can’t help but stare at a person with a zit on their face. This “red dot” can become a significant nuisance.

DLP

Digital Light Processing units are the newest and most interesting units. Unfortunately, we are not prepared to evaluate DLP units (we have not had a unit to evaluate). But we can give you some insights:

HD2 – This is the Texas Instruments digital light processing chip (their chip is composed of a million tiny mirrors to reflect light onto a screen like the tube projector units.

HD2+ – This is current TI chipset with improved reflectivity… better contrast and brightness.

HD3 – This is the upcoming chip from TI which provides significantly enhanced contrast and black (dark picture) resolution. This chip was previewed at CES2004 and it is a very good picture.

xHD3 – This is a superb TI chip that was also previewed at CES. Incorporated into a SAMSUNG prototype, it produced 1080p (yes – that is 1080progressive!)… the picture was absolutely awesome – completely equivalent to tube 1080i sets… in a much smaller cabinet.

We hope to have a specific series of articles discussing the TI DLP chipsets and their emergence as a significant improvement in HDTV technology in the very near future (Thanks TI!).

Commentary By: Greg Gibson - email