LED TV’s and monitors are part of the new High Definition generation. Quite simply, LED (Light Emitting Diode) technology uses individual backlights which in many cases can be tuned on or off in areas to allow for precision control of the lighting emitted from the TV screen or monitor. This differs from traditional backlighting which uses a CCFL (Cathode Fluorescent Lamp) that involves several fluorescent tubes placed horizontally across the screen. The enhanced benefits of LED technology allow for a sleeker screen design plus improved brightness potential, colour reproduction and viewing contrast.

The following guide will help you get to grips with LED technology so you can decide for yourself whether it deserves the must-have hype.

Types of LED Lighting

The first thing to understand is that there are two distinct types of LED TV screens or monitors based on how the LED backlighting is arranged:

Edge-lit screens

This type of TV screen or monitor has a row of LED backlights placed around the edges of the screen panel, which shine into a multi-layered diffuser panel creating a uniform view. Because the lights surround the perimeter of the screen instead of being behind it, edge-lit models allow for an ultra sleek design.

Full-matrix screens

These models have their LED lights arranged across the back of the display, which then feed through a diffuser panel to make the backlighting even. The most effective LED TV’s or monitors of this range have a feature called ‘local dimming’ or ‘smart dimming’ – this allows you to dim or switch off particular sections of the lighting elements while leaving other areas at full brightness. The result is enhanced picture contrast of black levels and other colours. It must be said that without this ability to fine tune the LED lighting to your tastes, LED TV’s are generally very similar to traditional LCD TV’s.

LED Viewing Quality

Colours

For on-point colour accuracy, LED TV’s and monitors with coloured backlighting are the best option. The display is still impressive however with the other type of LED lights which are white.

Definition & Contrast

As explained above, LED TV and monitors with the ‘local dimming’ feature gives you the power to control the backlighting arrangement for an improved picture quality in terms of definition and colour contrast. The result of being able to dim or switch off certain sections of the LED lights allows for darker blacks and enhanced definition while viewing dark-lit images. The other models that don’t have this feature are still high in viewing quality to the eye of the average person, but a true visual connoisseur will notice that uniform LED backlighting causes some areas of the screen to be better lit than others.

Angle of View

Because of the flat screen used by LED technology, it must be noted that this design suffers slightly from contrast degradation when the screen or monitor is viewed at angles of more than approximately 30 degrees from the centre. This issue has been significantly improved on over the past few years and has now advanced sufficiently to offer better viewing quality than plasma screens.

Size and Cost of LED TV’s

Televisions with LED backlights are currently on offer in sizes that range from 46 to 70 inches. While they generally cost a fair amount more than their traditional LCD television counterparts, many people are happy to pay the extra cost to have the best picture quality possible.

Life Expectation

As a general rule of thumb, TV manufacturers say their products have the longevity of approximately 100 000 hours. Since LED TV’s are quite new to the marketplace, this life expectation has not been fully confirmed as yet, however LED lights are known to last for a reasonably long period of time. LED backlighting technology is also said to suffer less degradation in colour over time than LCD models.

Power Usage

LED backlights offer better energy efficiency than CCFL-based backlights. It must be said however that a LED TV with the local dimming feature will use more electrical power than a traditional or edge-lit LCD TV that has the same screen size.
Whether you’re looking to buy a LED TV or LED monitor, the above information gives you the key facts about this new technology so you can make the right choice when shopping around for your viewing needs. As there are now an increasing amount of models available from different manufacturers, it’s crucial to do your research so you can be sure of finding the manufacturer and model that offers the best quality for your money.

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Purchasing a new PC monitor can sometimes be a headache with all of the technologies in pc monitors it can be a hard choice. PC monitor prices have decreased dramatically over the last 5 years and even the sizes have increased to allow higher resolutions and a better experience on the PC.

The first thing that comes to mind when deciding to buy an PC monitor is the size, there are a few options when it comes to the size of the monitor but you should get an idea of the size that you want. Most common users will settle for a 19″ monitor but if you want something larger you can get a higher resolution and more workspace on the screen. You will also have the option to choose from the widescreen monitor which can be helpful for some pc users.

Another aspect of choosing a PC monitor can be the manufacturer, some of the cheaper monitors will not look as crisp as others, here you will have to look at the pixel pitch, with a higher pixel count you will have less space in between the pixels which leads to a monitor that has a crisp picture. On the same subject the response time can also affect the monitor performance for gamers this can be an important aspect you can get these as low as 2ms but generally you will find them around 8ms. Another aspect you have to look at is the maximum resolution; if you are one who enjoys watching DVD’s or Bluray on your PC you will want a monitor with a high resolution to ensure you will have a crisp looking picture when watching movies. In general you will find most monitors offer a max resolution around 1920 x 1080 but the larger monitors offer more than this.

If you are looking to further increase the quality of your picture you will also want to get a monitor with a DVI cable, with a DVI cable this will give you even a better HD quality picture on your monitor. You will find that some monitors also have an HDMI input which is similar to DVI but it allows your monitor to support the higher resolutions. Otherwise you will have the regular VGA cable input. The last small aspect of your monitor is the movement, some people like to move their monitor to adjust their eye level you will find some are on pivot movements or you will find some don’t allow any movements so you may want to check if this is available if you like to adjust your monitor height or angle.

source: http://ezinearticles.com/?Understanding-the-Differences-in-PC-Monitors&id=5211098

Enabling crisp full-motion video

With the recent widespread use of PC and online games, and PCs equipped with DVD drives give users more opportunities to see moving images such as those in 3D games or action movies on screen. This increase in motion picture content means computer monitors must be able to display not only still images, but moving ones as well.

Manufacturers and IT publications often cite a fast response time as an indication that a display can play videos or games with little or no blurring. Hence, we would like to share with you what response time is, and how helpful it is in determining how well an individual LCD display can portray moving images.

Response time:
Why is it increasingly important for LCD applications?

If response time is slow, the transition from one picture (or frame) to another can produce an afterimage or blurring effect. This problem occurs not only when looking at motion pictures, but also during scrolling. For this reason, panels with faster response times are typically recommended for displaying moving images. Listed below are calculations for the liquid crystal response times that LCD displays meet, with consistent reliability, for various application standards. Response time is measured in milliseconds (ms, 1/1000 second). The shorter the time frame, the better the display quality.

 
Crisp Low Response Rate at Left and High Response Rate at Right.
Notice the blurring that occurs (right image) with High Response Rates.

LCD RESPONSE RATES
30 ms:1/0.030 = 33 fps meets specs of NTSC (30 fps), PAL (25 fps) or movie (24 fps) standards
16 ms:1/0.016 = 63 fps meets the spec of HDTV (60 fps) standards
12 ms:1/0.012 = 83 fps meets VESA flicker-free display with CRT of 72 fps and human-eye perception
8 ms:1/0.008 = 125 fps 3D PC games requirement
4 ms:1/0.004 = 250 fps Professional 3D PC games requirement
fps = frame (picture) per second

What is response time?

The transition time when LC materials are rotating on each of the required white/black or gray levels is called “rise time” and “fall time,” respectively. Normally, the transition time of 256 x 256 LC rotation levels needs to be measured. However, some companies don’t measure degree levels due to limitations of equipment capability.

Liquid crystals are rarely completely turned on or off. Instead, they cycle in between gray states. The following are two common methods some manufacturers use to measure response time:

On-Off response time Refers to the change time for screen pixels to turn from white to black (Tr) and from black to white (Tf) when the screen receives the signal. However, it does not indicate the transit time between gray levels.

Gray-to-Gray response time:

Since virtually all moving images include gray levels, and the frequency of gray-to-gray transitions is typically far greater than black-and-white transitions, we use the Gray-to-Gray response time definition to address the gray-to-gray transition time, allowing us to make an accurate assessment of a displays’ suitability to portray moving images.

At present, there is no accepted standard for the computation of Gray-to-Gray response time. However, as a company that emphasizes product reliability, most manufacturers insist on using the average to gauge performance, delivering better value to the end user.

How some manufacturers accelerate response times and guarantees reliable products:

Lower rotational viscosity liquid crystal materials and reduced cell gap thickness enhance “On-Off Response Time” performance.

To rapidly improve liquid crystal on-off response time, some manufacturers have developed products with lower rotational viscosity liquid crystal materials and reduced cell gap thickness during the first stage.

Many manufacturers overcome technical challenges such as non-uniformity and side effects caused by new LC materials in the LC-cell manufacturing process. Furthermore, new products undergo strict testing before launch.

Higher voltage with overdriving technology reduces the moving image’s “Gray-to-Gray response time.”

These quick response times modeled with new LC materials and a thick cell gap have earned such products much praise in the market in terms of capability and reliability, encouraging their makers to keep seeking new technologies for product upgrades. Models with overdriving technology have been integrated into many LCD displays, from manufacturers such as Acer, accelerating response times, especially for gray-to-gray.

Faster gray-to-gray response time via overdrive (OD) technology

The key benefit of OD technology is the clear improvement of the gray-to-gray level, which is the most important factor in the moving-picture viewing experience. Liquid crystal molecules respond faster to the high voltage that’s needed for black-white transitions than to the low voltage that’s needed for transitions between gray areas. Therefore, even though going from one grayscale level to another is less of a jump than going from black to white, the gray-to-gray transition time can actually take longer. Two LCD panels with the same black-white response times but with different gray-to-gray response times will have different moving picture playback capabilities.

As the figures below show, using an overdriving algorithm, LCD displays can reduce the deviation in the transition time and approach ideal performance. This significant improvement allows LCDs to deliver high-quality moving pictures for 3D games and videos.

A liquid crystal display (LCD) is a thin, electronic flat panel used to display information and images. It includes monitors for computers, televisions, instrument panels, and other devices ranging from aircraft cockpit displays, to every-day consumer devices such as video players, gaming devices, clocks, watches, calculators, and telephones. LCDs are simply everywhere now.

Its major features and benefits are: lightweight construction (compared to Plasma displays); portability (in the case of smaller displays); the ability to be produced in much larger screen sizes than were practical for older Tube (CRT) displays; and perhaps most important, its much lower power consumption.

Technically, an LCD display is an “electronically-modulated optical device” made up of any number of tiny pixels filled with liquid crystals and arrayed in front of a light source (backlight) or reflector to produce images in color.  The earliest discoveries leading to the development of LCD technology date from 1888. Today, tube CRT displays are almost a thing of the past!

Unfortunately, from time to time, a new LCD TV or Monitor will have a problem pixel.  This is where the physical crystal actually is stuck or frozen in place.  However, don’t panic, since these can frequently be fixed.

There are three basic types of problem pixels:

• a hot pixel (always on, usually white)
• a dead pixel (always off, black)
• a stuck pixel (one or more sub-pixels (red, blue or green) are always on or always off)

To solve a problem pixel, it is recommended to let the display fully warm up (leave on for at least a full day) – this alone can fix many problems, as the display expands due to warming and can free the pixel.  Always try this before calling for help.  Next, call the manufacturer’s technical support for other techniques that they might recommend – each manufacturer may have different solutions for their products.  There are also other techniques that you might try, but always be careful not to damage your display, as this might void your warranty. 

LCD Problem Pixel Policy
In the event that warranty service or an exchange is required, it is important to understand that every manufacturer has their own dead pixel policies, and that they should be contacted about solutions before requesting any exchange.  We want you to experience the best possible image on your LCD, so typically, an LCD TV or Monitor with 5 hot, dead, or stuck pixels would qualify for an exchange within the first 30 days of ownership after support efforts have been exhausted.  See the product warranty below for more information.

LCD Technology

How LCD’s Work

The twisted nematic (TN) is the most common type liquid crystal used in display applications such as LCD televisions, monitors and projectors. It is so named because it has a naturally twisted crystalline structure. This crystal reacts to electric currents in predictable ways, such as untwisting to varying degrees depending on the voltage of the current to which it is exposed. The main difference between plasma and LCD technology is that LCD pixels don’t emit light. As with plasma technology, an LCD pixel is comprised of three sub-pixels in the elementary colors. Because they don’t emit light, LCD displays need white backlighting. The light emitted by the backlighting passes through the liquid crystal and is then colored by a filter. Each subpixel has the same characteristics; only the color of the filter changes depending on the pixel. The liquid crystal of each subpixel can be controlled electrically like a valve; the amount of light allowed to pass through the crystal governs how much red, green and blue is emitted for each pixel. Active matrix LCDs employ thin film transistors (TFTs),m or tiny switching transistors and capacitors arranged in a matrix on a glass substrate, to direct electric charges down columns to reach a particular pixel. In turn, this causes the liquid crystals to untwist and display a predetermined amount of light generated by the light source – usually a fluorescent bulb located in back of them. By exploiting a combination of red, green, and blue subpixels of various intensities (or gray scales), a single pixel triad can reproduce approximately 16.8 million colors.

LCD Pluses

LCDs offer higher resolutions than plasmas of the same size. They also have excellent image stability. In other words, you can sit close without experiencing eye fatigue. Additionally, LCDs boast a longer lifetime than plasma televisions – on average about 50,000 hours versus 30,000 hours. Also, If you’re contemplating a home entertainment setup involving a PC–perhaps running Windows XP Media center Edition – or other activities involving text as well as graphics, you’ll get a crisper, brighter image from an LCD. LCDs are also space-efficient and because they operate at much cooler temperatures cost less per hour than plasma televisions. The smaller and better transistors found in LCDs give them another advantage over plasma – higher resolution.

LCD Minuses

LCD viewing angles cannot match those of plasma displays. You tend to see some brightness and color shift when you’re sitting at too far an angle from your LCD, while a plasma’s picture remains fairly solid. LCDs also have lower contrast ratios than plasmas and are not as good at rendering deep blacks. Additionally, they are not as good as plasmas in tracking motion and fast-moving objects may exhibit what is called, lag artifacts.

LCD Uses

The area where LCD reigns supreme over any other flat-panel displays is, of course, computers. LCD monitors can now be used for most applications including games, office applications, and photo retouching. But it’s another story for television. LCD is lagging behind plasma, but it’s available in more reasonable display sizes. In terms of absolute video quality, plasma is still tops, because it offers blacks as good as what CRTs can display, exceptional viewing angles, and unmatched color. However, LCDs are closing the gap little by little with technologies that are constantly being refined.

Plasma TVs are still around, though for how much longer is anyone’s guess.  But great deals may mean giving plasma a chance.  So here is a basic introduction into Plasma TVs.

Plasma Technology

Plasma History
Although you may think plasma technology is a recent phenomenon, the science has been around since 1960, and the first plasma prototype appeared back in 1964. While a handful of major manufacturers were interested in plasma technology at the outset, the absence of industrial outlets caused the entire industry to nearly grind to a halt by the late 1980s. However, plasma research continued in Japan, where the first commercial models hit the market in the early 1990s. Today most major consumer electronics manufacturers offer plasma televisions.

Plasma screens, as the name suggests, use a matrix of tiny gas plasma bubbles coated by phosphor and charged by precise electrical voltages to create a picture. Plasma technology operates on the premise that each subpixel within a plasma display is a microscopic fluorescent lamp that emits one of the primary colors (red, green or blue). Technicians are able to create a multitude of tints by varying the intensity of the light from these three subpixels. When it’s time to display an image signal (RGB or video), a digitally controlled electric current flows through the flat screen, causing the plasma inside designated bubbles to give off ultraviolet rays. This light in turn causes the phosphor coatings to glow the appropriate color. The millions of RGB bubbles glowing and dimming combine to make a rich, vivid image. Because the light emitted by the plasma is ultraviolet radiation, which is invisible to humans, it must be changed into a visible form of energy. To achieve this transformation, the walls of the plasma tube are coated with a UV-sensitive powder that emits white light. This powder, often called a phosphor, is known as a scintillator – a material that converts one type of radiation to another. CRTs also contain scinitillators that convert the electron beams into visible red, green or blue light.

Plasma Pluses
The most striking advantage that plasmas currently over LCD televisions is their availability in the largest screen formats. However, it won’t be long before some manufacturers produce LCD screens that will be comparable in size to many plasmas. Currently, on an inch by inch basis, plasmas are less expensive than LCDs. Additionally, plasma contrasts are also superior to those of LCDs, and equal to the best CRT televisions. Plasma TVs are quite versatile; capable of displaying full HDTV and DTV signals as well as XGA, SVGA and VGA signals from a computer. Furthermore, plasma televisions present a much wider range of richer colors due to their huge choice of scintillators. High-end plasma screens can display 16.77 million colors, providing superb realism with exceptionally subtle gradations among colors. In fact, color saturation represents one of the most dramatic advantages that plasma screens have over other display technologies.

Plasma Minuses
On the negative side, the large size of the plasma pixels means that plasma televisions are restricted in size to at least 32-inches diagonal in order to achieve competitive resolutions. Plasma sets also encounter some image quality problems stemming from the nature of their pixels. Because plasma pixels need an electrical discharge in order to emit light, a pixel must be lit or unlit, but has no intermediate state. Consequently, plasma manufacturers employ a method called PCM (Pulse Code Modulation) to control brightness. With PCM, a pixel is lit frequently to attain brightness and less often to attain a darker shade. This works well for medium and bright colors, but it’s often difficult to distinguish between two similarly dark shades. PCM technology creates a uniform image if the viewer if far enough from the panel, but some discomfort at close distances. Plasma pixels are also prone to burn-in, a phenomenon also found in CRT screens. Burn-in occurs when the same image is projected too long and becomes permanently imprinted on the phosphor because of premature aging of the scintillators. This isn’t a problem under normal use, because the images projected change constantly. However, in certain business applications, where the same channel is used on the screen all the time, issues can arise. For example, a network’s logo can become burned into the display. And when a plasma screen is used for static advertising displays, a fixed image projected constantly can become burned into the panel.

Uses for Plasma TVs
Plasma displays are found mostly in high-quality, large-format video systems. Their big size and video performance make them excellent for viewing DVDs, high definition or otherwise. Plasma is traditionally positioned at the high-end sector of the market, where the issues of high cost, phosphor aging and high power consumption are secondary to performance and quality.