LCD (Liquid Crystal Display) televisions represent the most popular form of image production technology in commercial televisions. LCD replaced CRT as the dominant technology in televisions in 2003 and counted sales of nearly 43M in the first quarter of 2012 alone. LCD TVs are dramatically thinner and brighter than equivalent CRT televisions. With advances in technology and lower cost of production, large scale LCD panels can be made for relatively cheap. Besides televisions, LCD technology finds use in a number of other devices, including mobile phones, tablets, and digital camera screens.
About LCD Televisions
A LCD display panel responds to electric currents. Pictures are displayed by blocking or allowing light through. Each pixel represents a solution of TN (Twisted Nematic) liquid crystals sandwiched between two planes of polarised glass, such that the intensity of light passing through can be manipulated. Depending on the amount of voltage passing through the matrix, the TN crystals twist or untwist, allowing light to pass through, making it possible to reproduce images.
Light in a LCD television may be provided by an array of cold cathode fluorescent lamps (CCFLs) or a series of LED lights. This is the reason why LCD is called a 'backlit' display technology. TN liquid crystals basically act as shutters equipped with a colour filter that blocks out all but the red, green, and blue (RGB) component of light. Any colour may be produced by mixing these three basic RGB colours in the correct proportion. The TN liquid crystals are sensitive to electric currents. As current passes through the display, selective 'shutters' open and close, enabling the production of images on screen. LCD displays were first developed in the 1980s for use in computer screens.
These earlier displays suffered from low refresh rates, high cost and poor image quality. Subsequent research in the field, propped by the inefficiencies of the dominant CRT technology led to several breakthroughs in early half of this century. By the mid-2000s, LCD television prices were at par with CRT, and lower than the competing plasma technology, making LCD the dominant technology in commercial televisions.
Buying LCD Televisions
LCD televisions vary wildly in price and quality, depending on the underlying technology. Physical specifications alone may not be enough to give an idea of the image quality of a LCD television; it is often beneficial to compare actual performance first-hand. That said, there are several factors that must be considered when purchasing a LCD television.
LCD Television Screen Resolution
Resolution represents the maximum number of pixels displayed by the LCD television. It is an important indicator of quality in LCD TVs. The higher the resolution, the better the picture quality provided the picture input device (a Blu-Ray player, digital set-top box or gaming console) also supports the higher resolution. LCD television resolution is denoted by the number of vertical pixels supported by the screen. Thus, 1080p (more on 'p' below) means the screen has a minimum vertical pixel count of 1080. Broadly speaking, LCD TV screen resolutions may be categorised as follows:
576p resolution has almost been deprecated but may be found in small screens (23 inches and below). Screens of this resolution are often used in non-television devices, however, such as digital picture frames, digital clocks, etc.
720p resolution is classified as 'HD', although it has largely been replaced by the higher 1080p resolution in most televisions sold today. TVs below 40-inches may still use 720p resolution, however.
1080p resolution is often called 'True HD'. This is the highest resolution in current commercial grade televisions. To take full advantage of 1080p LCD televisions, it is important to have a supporting input source capable of 1080p resolution.
Although 1080i is the same resolution as 1080p, the picture quality is markedly poorer. The 'i' in 1080i stands for 'interlaced' scanning which results in quality loss.
Interlaced and Progressive Scanning Explained
In the above table of LCD television resolution, the 'p' stands for 'progressive scanning', while 'i' stands for 'interlaced scanning'. Progressive scanning means that the TV displays images by scanning every horizontal row of pixels. Televisions with interlaced scanning, on the other hand, display images by scanning only every second row of pixels. While this reduces power consumption and improves refresh rate, interlaced scanning results in a markedly poorer image quality as compared with progressive scanning.
LCD Television Aspect Ratio
Aspect ratio refers to width to height proportion of a TV screen. An aspect ratio of 16:9 means that there 16 inches of width for every 9 inches of height on the screen. Common aspect ratio specifications of LCD televisions can be classified as follows:
4:3 (Standard TV)
4:3 aspect ratio means that there are four inches of width for every three inches of height. This is the aspect ratio of standard, non-HD televisions. Few LCD televisions sold today support 4:3 aspect ratio.
5:4 aspect ratio may be found in some computer monitors but is very rare in LCD televisions. Some older LCD TV models may support 5:4 ratio.
16:9 is the standard aspect ratio of most LCD televisions. It is also called 'widescreen' ratio. Most modern media devices such as Blu-Ray players, video game consoles and digital set-top boxes support 16:9 aspect ratio.
When purchasing LCD televisions, it is important to consider the aspect ratio supported by the input device as well as the LCD television. If the input device supports only 4:3 ratio, and the television can only display pictures in 16:9 ratio, the resultant image might appear bloated or stretched. Most modern LCD televisions have the option to switch aspect ratios, however, making them compatible with older, non-widescreen supporting media devices.
LCD Television Screen Size and Viewing Distance
Screen size is one of the single most important factors in LCD television purchase decisions. The quality of the viewing experience, however, is affected as much by the viewer's distance from the screen as by the actual screen size. Although bigger screens arguably offer a more enjoyable experience, smaller screens may suffice in certain settings. Broadly speaking, viewing distance and screen size correlates as follows:
Screen Size (in inches)
Viewing Distance (in feet)
Appropriate for use as computer monitors and small study rooms.
Screens between 27 to 32 inches are good in small bedrooms.
Screens up to 40 inches in size are good for large bedrooms and small living rooms.
42 inches and up
Screens larger than 42 inches should have a viewing distance of at least 10 feet and above between them. These are useful only in large living rooms and bedrooms.
LCD Television Contrast Ratio
Contrast ratio refers to the difference between the whitest and darkest part of an image. Contrast ratio plays an important role in determining picture quality. Typically, the higher this ratio, the better the final image quality. Contrast ratio is typically expressed as the ratio of the brightest white and the darkest black. Thus, a contrast ratio of 3,000:1 means that the whitest white is 3,000 times brighter than the darkest black. There are no industry standards for measuring contrast ratios. Consequently, most manufacturers use internal standards without external validation, which can often mislead customers. Therefore, contrast ratio must be used as a measuring specification only when comparing televisions from the same manufacturer. Contrast ratio can be broadly split into two categories:
Static Contrast Ratio
Static contrast ratio is the contrast ratio of the screen at any given time, regardless of whether the image on screen is in motion or not. Static ratio is a better indicator of image quality than dynamic contrast ratio.
Dynamic Contrast Ratio
Dynamic contrast ratio is the overall contrast ratio produced by any LCD television. It may be called the average of the contrast ratio, rather than the ratio at any single instant.
LCD Television Response Time
Response time refers to the time it takes for a pixel to go from switched off (black) to on (white) state. The lower the response time, the faster the picture changes on-screen. This is an especially important performance factor when viewing fast-changing action (such as a race) or playing video games. Response time is often expressed as refresh rate. Refresh rate measures the number of times the screen is redrawn each second. It is expressed in Hertz. Thus, a LCD television with a refresh rate of 60Hz means that the screen is redrawn 60 times every second. Typically, the higher the refresh rate, the better the television performance. Older LCD television models usually have a refresh rate of 60Hz, though newer models being sold today may have a refresh rate as high as 600Hz. Most televisions in the market today have a refresh rate between 120Hz to 240Hz. If buying a LCD television explicitly for displaying fast moving action, a refresh rate in excess of 200Hz is highly recommended.
LCD Television Ports and Connections
A LCD television needs to be compatible with existing media devices. Consequently, a wide selection of ports to accommodate different media devices is highly desirable. Some of the ports and connections commonly found in LCD televisions are:
HDMI is the standard input for most high definition media devices, including Blu-Ray players, video game consoles and HD digital TV boxes.
Component cables are usually used to connect DVD players or speakers to the television. This consists of three cables - one for video, and two cables for stereo audio.
A coaxial port accommodates a cable wire. This is an old standard that is quickly being replaced by digital TV boxes.
DVI port is used to connect the television to a computer monitor. While not necessary, it can extend the television's functionality. Some computer monitors sold today come equipped with HDMI ports, eliminating the need for DVI ports.
An optical port is used to connect high-end audio to the LCD television. It is usually used in Dolby 5.1 Surround Sound Systems.
Buying LCD Televisions on eBay
A LCD television represents a significant investment. For best prices and large selection of products, LCD televisions can be bought from eBay. To buy LCD TVs on eBay, go to the eBay UK homepage and search for LCD television in the Sound and Vision category . The search results can then be filtered according to various criteria, such as screen size (from less than 20 inches to 50 '' -60" ), by brand ( Samsung , LG , Toshiba , 1080p , etc.), and additional features such as downloadable Smart TV apps , active 3D and Built-in Digital Tuner .
With steadily reducing prices, LCD televisions have overtaken CRT TVs as the most popular technology in commercial TVs. LCD TVs are lightweight, bright, and offer superb picture quality at affordable prices. Resolution, screen size, aspect ratio, contrast ratio and refresh rate are some important considerations when buying LCD televisions. LCD TVs can be bought from eBay which has a wide selection of new and used products at attractive prices.