LCD, or liquid crystal display, televisions use a unique form of technology to produce their display, and although early models had a number of technological issues, those issues have largely been overcome, and these days there are excellent quality LCD TVs available from virtually every manufacturer of electronics in the world. The earliest models of LCD televisions often had problems with ghosting, especially when displaying fast action or fast moving imaging, and these early televisions were best viewed straight on or from a slight angle. These early problems have been overcome by advances in technology, and LCD and plasma TVs are making serious inroads on the traditional CRT (cathode ray tube) television market. The prices of LCD televisions have come down quite a bit as well, even as the technology they use has continued to improve. These days the least expensive, small screen LCD TVs can often be purchased for a couple hundred dollars, while the largest displays sell for several thousand dollars. There are even larger LCD displays on the market, as large as 65 and even more, that may sell for $10,000 or more. If price is no object it is possible to find an LCD TV for virtually any taste. The advent of these large screen LCD TVs is another indication of how much the technology has improved in a short period of time. When LCD technology was first being developed, the conventional wisdom was that it would be suitable only for small size televisions, and that the LCD technology would not be able to compete with plasma screens for larger sets. These days, however, ever larger LCD TVs are being developed and introduced, by the likes of Sony, Sharp, Samsung, Phillips and others. The modern LCD TV is good for much more than watching TV, and the best sets on the market come with a multisystem tuner, which allows the machine to display not only the NTSC format common throughout North America, but the PAL and SECAM signals that are common in other parts of the world. In addition, many LCD TVs include a step down and step up transformer which can automatically use either 110 or 250 volt AC current, as well as universal grounded adapter plugs for added versatility. In addition, virtually all modern LCD TVs on the market today are capable of displaying the latest HDTV (high definition television) and DTV (digital television) signals, and most can also be used as a computer monitor, by connecting them to a VGA or DVI signal. Those TV shoppers planning to use their new LCD TV as a monitor should be cautious, however, since the quality of the resolution can vary widely between brands and models. LCD TV Considerations Those in the market for an LCD TV to replace a traditional CRT TV should be aware of the differences in the technology, and what those differences mean in terms of viewing pleasure and lasting value. LCD televisions based on the PVA and S-PVA LCD panel are able to deliver a very good viewing angle at up to 140 degrees, and they also can provide a good contract ratio for viewing both light scenes and dark ones. The downside of the PVA and S-PVA technology is that they often have problems with ghosting when the scene moves between different shades of dark. Traditional CRT televisions to not have this problem with ghosting since the phosphor contained in the CRT is charged by the strike of a beam of electrons, and it emits most of the light in a fast period of time, generally less than 1 millisecond, compared to a refresh period of about 20 milliseconds. For an LCD TV, each pixel emits light of a set intensity for a period of about 20 milliseconds, in addition to the time it takes to switch to the next state, which is typically between 12 and 25 milliseconds. This response time, also known as the response time, can be shortened by the design of the panel, and by using overdriving technology, but the response time can only be cut down to the length of the refresh period. Getting the response time equal to the refresh period is generally sufficient for watching films and television programs, but for videos shot at 50 or 60 frames a second there can still be some ghosting issues with some LCD TVs. Fortunately, there are a number of emerging technologies within the world of the LCD TV, and these technologies promise to eliminate some of the ghosting and other issues that have been encountered by owners of these TVs. The first solution on the horizon is to make the backlight of the LCD panel fire during a period of time that is shorter than the refresh period. The goal is to make this period of time as short as possible, and to time it for when the pixel has already settled to its intended level of brightness. This technique, however, also introduces the problem of flicker that is so familiar to users of CRT computer monitors. This flicker problem occurs because the human eye is able to see flicker at the typical 50 or 60Hz refresh rates used in this technology. Another emerging response to the problem is to double the refresh rate of the LCD TV, and then to reconstruct the intermediate frames using a variety of motion compensation techniques. This second method is being extensively studied on the new high end televisions currently being designed in Europe. No matter what type of LCD TV technology you decide to buy, however, it is important to shop around for the best possible price. These days even discount retailers often sell some very good LCD TVs, and of course many electronics stores are virtually replacing their existing stock of CRT TVs with the newest in LCD and plasma screen technology. As with any major purchase, it is vital to shop around for the best deal, and to read the reviews of each model carefully. As with any piece of electronic equipment, the quality of an LCD TV can vary quite widely from model to model and brand to brand. For more information see: http://www.planetomni.com |
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