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LCD Television

Buying an LCD Television An Introduction to LCD TV

LCD televisions offer two major advantages. Firstly they are easier to the eye than a conventional CRT (cathode ray tube) set, with brighter displays, improved contrast and not flicker. Secondly, they have a higher inherent resolution than plasma TVs of similar size and are thus ideal for high definition TV (HDTV). So how does it work? The technology is quite complex and is constantly improving. It uses the fact that liquid crystals are, by default, in a twisted state. Applying electric current to them allows them to admit light through. In basic terms, a light source shines through a liquid containing these crystals which is contained between two polarised screens. Applying the correct current to the relevant parts of the display creates the desired picture.

Key Features and Points to Consider

Refresh Rate

This is also referred to as the 'frequency rate' - the number of times the picture is updated per second. Most conventional CRT TVs operate at 50Hz with some people observing flickering. LCD TVs run at a higher rate, giving a clearer picture.

Aspect Ratios

Until widescreen high-definition TV becomes the standard, many programmes will still be broadcast in the traditional 4:3 aspect ratio. Most LCD TVs are built to operate in 16:9 (widescreen) format although 4:3 is still commonly found. When given a 4:3 picture, an LCD TV will adjust the picture to fit the screen by stretching or zooming the image.

Screen Size

More pixels means more transistors (three per pixel) and colours can appear slightly faded in larger models. LCD TVs have therefore traditionally been at the smaller end of the scale, in the range 14 to 19 inches. The technology continues to improve and many models over 30 inches are emerging although 40 inches plus is still rare.

Depth

A major benefit of LCD TVs is the physical depth of the set. Most are less than 3 inches deep and can be hung on a wall or suspended from the ceiling.

Active or Passive

Matrix LCD TVs at the lower end of the budget scale tend to use a passive matrix system. This has a conductor grid with pixels located at each intersection. Current is sent across two conductors on the grid to control the light for any pixel. The tends to result in a slower response time and less precise, with less contrast, some ghosting and blur. Active matrix sets, also referred to as thin film transistor (TFT) sets, are more expensive because they target electrical charges at specific pixels. This improves the screen refresh time, contrast and clarity.

Other Uses

LCD TVs are well suited to for use as a computer screen, with sharp display of text and graphics. Accordingly, LCD sets often include connections for composite, S-video, component video and one or more RGB SCART inputs.

Integrated tuners

Higher end models tend to include integrated digital TV receivers (IDTV) and speakers, reducing the number of boxes and connections needed in the system.

Power consumption

Another key advantage of LCD technology is lower power consumption. This is particularly beneficial with larger screen sizes. LCD screens consume up to 30% less power than their plasma equivalents.

Resolution and Picture Quality

Most people assume that a higher resolution means a better picture. Not true. VGA quality is found on most standard TVs. But LCD TVs may also have XGA (1024x768 pixels) or, the widescreen versions may offer W-XGA (1280x768 pixels). As we have seen above, there are a good many factors that affect picture quality. Check the picture itself. How realistic are flesh tones? How good is the contrast in dark scenes? How well is fast motion displayed?