What’s an LCD HDTV?
LCD Television BASICS (Liquid Crystal Display)
In 2007, LCD televisions surpassed sales of CRT-
Ok let’s cover some of the basics here. A Liquid crystal display is used in lots of devices. Most common devices that use LCD displays are clocks, microwaves, car stereo systems, and yes HDTV’s.
If your looking for an HDTV to last a good while than LCD is a great way to go! Most LCD HDTV’s are rated for 60,000 hours, up to 80,000 hours depending on the manufacture and rated life span of the bulb. Most LCD HDTV’s will last longer than a Plasma TV. An LCD HDTV will usually last as long as the bulb inside the TV. Just like any bulb dims over a period of years, so will an LCD HDTV Bulb. To calculate the years figure out how many hours you watch per day and multiply that by 365. Then divide that by the rated hours of the LCD TV you have or the one your going to purchase. Assuming your electronics, circuits, and microchips out last the LCD panel your LCD TV should be rated around 60,000 hours.
What are you going to be doing with your HDTV? Movies, video games, watching basic TV or an alternate computer monitor?
Whatever your needs are will determine what features are more important than others. If you are going to be watching mostly High Definition movies & gaming then screen resolution, refresh rate, response time and contrast ratio should be some of your considerations. If your going to be using your HDTV for basic TV viewing then you might be more concerned with screen size and price. If your going to be using your HDTV for an alternate computer monitor you might be more concerned with it’s input options, screen resolution and aspect ratio. But whatever your heart desires there is an HDTV solution out there to fit you need and budget. We will help you get there!
Okay, Lets get our first glimpse at what Specifications are going to be a deciding factor in buying your new HDTV.
Most LCD HDTV’s come in two different aspect ratios 4:3 and 16:9. Depending on what you will be using your HDTV for should determine what aspect ratio you decide to go with. 4:3 is your standard viewing size “regular TV size” 16:9 is your wide screen size “movie screen dimensions”. You can make your decision based on a few factors. If you have an entertainment center that is designed for a TV with a 4:3 aspect ratio you will have to sacrifice screen size if you want to put a 16:9 aspect ratio HDTV in that same entertainment center. If you are planing to upgrade your entertainment center when you upgrade your HDTV then you should decide on what size TV you want first and then find a entertainment center or HDTV stand that is tailored fit to your new HDTV. Keep in mind that most HDTV’s on the market are 16:9 aspect ratio. So finding exactly what you want in a 16:9 aspect ratio is more likely.
If you decide to stay with your current entertainment center then you should measure it and shop your new HDTV according to you size requirements.
Native Screen resolution most manufactures offer 3 different types resolutions 1080p (Progressive Scan) which equates to 1,920 x 1,080 pixels “This is the way to go if you can afford it”, next in line is 720p (Progressive Scan) which equates to 1280 x 720 pixels. 3rd in line is 1080i which equates to 1,920 x 1,080 (interlaced) pixel resolution but conveys the images in an interlaced format (which gives it the “I” in 1080i for interlaced). Most HDTV channels broadcast in the last 2 resolutions listed, 720p or 1080i is the standard broadcast formats for most cable, direct TV™, and satellite feeds, the deciding factor should include your price range and what type of media you will be viewing.
Refresh Rate is the rate at which the signal refreshes per second. The faster the refresh rate the sharper the action and the image will be in fast paced media such as football, action movies, etc. If your mostly going to be using your new HDTV for TV shows than a lower refresh rate will be fine. But for you gamers and High Definition action movie fans a refresh rate of 60 Fps to 120 Fps “Frames Per Second” will be more desirable because the higher refresh rate keeps the image transition looking smooth.
Response time is another very important factor you need to consider. Response time represents the amount of time it takes for one pixel to go from active “black” to inactive “white” and back to black again. It’s the speed at which an LCD panels crystals “twist” to block and allow light to pass through. This process is measured in (ms) milliseconds, the lower the number the faster it can change between active (black) and inactive (white) Pixels. Another words the lower the milliseconds, the lower the response time. The clearer the picture will be on the screen. You gamers, sports fans & action movie fans should go with a lower response time. Slower response times range around 20 milliseconds, faster response times are usually around 8 TO 2 milliseconds. This millisecond factor can impact your purchase price by inches or miles. Shop for a happy medium based on your needs and budget.
Example: Contrast ratio will read something like, 300:1 or 500:1, and can even go as high as 10000:1 and getting higher as technology advances! The higher the contrast ratio “left number” the blacker the blacks will be to whites and will result in fewer areas that look gray but are suppose to be black. Remember this is an important number but you should always judge by your eyes. Simply put, what looks good is good! And use the contrast ratio as a guide to get started in the right direction.
I would suggest determining your price range first, selecting your desired screen size second. Then go to your local HDTV store and view your desired screen size, Doing this will assure you get the right size HDTV with the best looking picture for your budget! Remember a good balance between HDTV features is the smart way to go! Check out our expert review matrix for great combinations of features, prices, sizes Etc.
Viewing Angle of your LCD is a factor, not as important as most other factors, but a factor. I would suggest not making this a big deal, you can usually sit at least 72 degrees off the axis and still see a perfect picture. Although most manufactures state that there viewing angle is much more than this you will notice little decrease in color saturation, brightness and contrast in the picture. Most LCD’s of today are pretty much equal in this arena. But the question is will you actually need it?
LCD televisions produce a colored image by selectively filtering a white light. The
light is typically provided by a series of cold cathode fluorescent lamps (CCFLs)
at the back of the screen, although some displays use white or colored LEDs instead.
Millions of individual LCD shutters, arranged in a grid, open and close to allow
a metered amount of the white light through. Each shutter is paired with a colored
filter to remove all but the red, green or blue (RGB) portion of the light from the
original white source. Each shutter–filter pair forms a single sub-
Liquid crystals encompass a wide range of (typically) rod-
LCD shutters consist of a stack of three primary elements. On the bottom and top of the shutter are polarizer plates set at (typically) right angles. Normally light cannot travel through a pair of polarizers arranged in this fashion, and the display would be black. The polarizers also carry the directors to create the twisted structure aligned with the polarizers on either side. As the light flows out of the rear polarizer, it will naturally follow the liquid crystal's twist, exiting the front of the liquid crystal having been rotated through the correct angle that allows it to pass through the front polarizer. LCDs are normally transparent.
To turn a shutter off, an electrical voltage is applied across it from front to back.
When this happens, the rod-
Several other variations and modifications have been used in order to improve performance
in certain applications. In-
A typical shutter assembly consists of a sandwich of several layers deposited on two thin glass sheets forming the front and back of the display. For smaller display sizes (under 30 inches), the glass sheets can be replaced with plastic.
The rear sheet starts with a polarizing film, the glass sheet, the active matrix
components and addressing electrodes, and then the director. The front sheet is similar,
but lacks the active matrix components, replacing those with the patterned color
filters. Using a multi-
The critical step in the manufacturing process is the deposition of the active matrix components. These have a relatively high failure rate, which renders those pixels on the screen "always on". If there are enough broken pixels, the screen has to be discarded. The number of discarded panels has a strong effect on the price of the resulting television sets, and the major downward fall in pricing between 2006 and 2008 was due mostly to improved processes.
To produce a complete television, the shutter assembly is combined with control electronics and backlight. The backlight for small sets can be provided by a single lamp using a diffuser or frosted mirror to spread out the light, but for larger displays a single lamp is not bright enough and the rear surface is instead covered with a number of separate lamps. Achieving even lighting over the front of an entire display remains a challenge, and bright and dark spots are not uncommon.
In a CRT the electron beam is produced by heating a metal filament, which "boils"
electrons off its surface. The electrons are then accelerated and focused in an electron
gun, and aimed at the proper location on the screen using electromagnets. The majority
of the power budget of a CRT goes into heating the filament, which is why the back
of a CRT-
The lack of vacuum in an LCD television is one of its advantages; there is a small
amount of vacuum in sets using CCFL backlights, but this is arranged in cylinders
which are naturally stronger than large flat plates. Removing the need for heavy
glass faces allows LCDs to be much lighter than other technologies. For instance,
the Sharp LC-
LCD panels, like other flat panel displays, are also much thinner than CRTs. Since
the CRT can only bend the electron beam through a critical angle while still maintaining
focus, the electron gun has to be located some distance from the front face of the
television. In early sets from the 1950s the angle was often as small as 35 degrees
LCDs can, in theory, be built at any size, with production yields being the primary
constraint. As yields increased, common LCD screen sizes grew, from 14 to 30", to
42", then 52", and 65" sets are now widely available. This allowed LCDs to compete
directly with most in-
LCDs are relatively inefficient in terms of power use per display size, because the
vast majority of light that is being produced at the back of the screen is blocked
before it reaches the viewer. To start with, the rear polarizer filters out over
half of the original un-
For these reasons the backlighting system has to be extremely powerful. In spite
of using highly efficient CCFLs, most sets use several hundred watts of power, more
than would be required to light an entire house with the same technology. As a result,
LCD televisions end up with overall power usage similar to a CRT of the same size.
Using the same examples, the KV-
Modern LCD sets have attempted to address the power use through a process known as "dynamic lighting" (originally introduced for other reasons, see below). This system examines the image to find areas that are darker, and reduces the backlighting in those areas. CCFLs are long cylinders that run the length of the screen, so this change can only be used to control the brightness of the screen as a whole, or at least wide horizontal bands of it. This makes the technique suitable only for particular types of images, like the credits at the end of a movie. Sets using LEDs are more distributed, with each LED lighting only a small number of pixels, typically a 16 by 16 patch. This allows them to dynamically adjust brightness of much smaller areas, which is suitable for a much wider set of images.
Another ongoing area of research is to use materials that optically route light in
order to re-
Several newer technologies, OLED, FED and SED, have lower power use as one of their
primary advantages. All of these technologies directly produce light on a sub-
For 60 frames per second video, common in North America, each pixel is lit for 17
ms before it has to be re-
A major improvement, pioneered by NEC, led to the first practical LCD televisions. NEC noticed that liquid crystals take some time to start moving into their new orientation, but stop rapidly. If the initial movement could be accelerated, the overall performance would be increased. NEC's solution was to boost the voltage during the "spin up period" when the capacitor is initially being charged, and then dropping back to normal levels to fill it to the required voltage. A common method is to double the voltage, but halve the pulse width, delivering the same total amount of power. Named "Overdrive" by NEC, the technique is now widely used on almost all LCDs.
Another major improvement in response time was achieved by adding memory to hold
the contents of the display – something that a television needs to do anyway, but
was not originally required in the computer monitor role that bootstrapped the LCD
industry. In older displays the active matrix capacitors were first drained, and
then recharged to the new value with every refresh. But in most cases, the vast majority
of the screen's image does not change from frame to frame. By holding the before
and after values in computer memory, comparing them, and only resetting those sub-
Together, along with continued improvements in the liquid crystals themselves, and by increasing refresh rates from 60 Hz to 120 and 240 Hz, response times fell from 20 ms in 2000 to about 2 ms in the best modern displays. But even this is not really fast enough because the pixel will still be switching while the frame is being displayed. Conventional CRTs are well under 1 ms, and plasma and OLED displays boast times on the order of 0.001 ms.
One way to further improve the effective refresh rate is to use "super-
Even in a fully switched-
This lack of contrast is most noticeable in darker scenes; in order to display a
color close to black, the LCD shutters have to be turned to almost full opacity,
limiting the number of discrete colors they can display. This leads to "posterizing"
effects and bands of discrete colors that become visible in shadows. Which is why
many reviews of LCD TV's mention the "shadow detail". For contrast, the highest-
Since the total amount of light reaching the viewer is a combination of the backlighting
and shuttering, modern sets can use "dynamic backlighting" to improve the contrast
ratio and shadow detail. If a particular area of the screen is dark, a conventional
set will have to set its shutters close to opaque to cut down the light. However,
if the backlighting is reduced by half in that area, the shuttering can be reduced
by half, and the number of available shuttering levels in the sub-
However, it should be noted that the area of the screen that can be dynamically adjusted
is a function of the backlighting source. CCFLs are thin tubes that light up many
rows (or columns) across the entire screen at once, and that light is spread out
with diffusers. The CCFL must be driven with enough power to light the brightest
area of the portion of the image in front of it, so if the image is light on one
side and dark on the other, this technique cannot be used successfully. Displays
backlit by full arrays of LEDs have an advantage, because each LED lights only a
small patch of the screen. This allows the dynamic backlighting to be used on a much
wider variety of images. Edge-
The massive on-
Color on an LCD television is produced by filtering down a white source and then selectively shuttering the three primary colors relative to each other. The accuracy and quality of the resulting colors are thus dependent on the backlighting source and its ability to evenly produce white light. The CCFL’s used in early LCD televisions were not particularly white, and tended to be strongest in greens. Modern backlighting has improved this, and sets commonly quote a color space covering about 75% of the NTSC 1953 color gamut. Using white LEDs as the backlight improves this further.
In September 2009 Nanoco Group announced that it had signed a joint development agreement with a major Japanese electronics company under which it will design and develop quantum dots for use in LED backlights in LCD televisions. Quantum dots are valued for displays, because they emit light in very specific gaussian distributions. This can result in a display that more accurately renders the colors that the human eye can perceive. Quantum dots also require very little power since they are not color filtered.
Passive matrix LCD’s first became common in the 1980’s for various portable computer roles. At the time they competed with plasma displays in the same market space. The LCD’s had very slow refresh rates that blurred the screen even with scrolling text, but their light weight and low cost were major benefits. Screens using reflective LCD’s required no internal light source, making them particularly well suited to laptop computers.
Refresh rates were far too slow to be useful for television, but at the time there was no pressing need for new television technologies. Resolutions were limited to standard definition, although a number of technologies were pushing displays towards the limits of that standard; Super VHS offered improved color saturation, and DVDs added higher resolutions as well. Even with these advances, screen sizes over 30" were rare as these formats would start to appear blocky at normal seating distances when viewed on larger screens. Projection systems were generally limited to situations where the image had to be viewed by a larger audience.
Nevertheless, some experimentation with LCD televisions took place during this period.
In 1988, Sharp Corporation introduced the first commercial LCD television, a 14"
model. These were offered primarily as boutique items for discerning customers, and
were not aimed at the general market. At the same time, plasma displays could easily
offer the performance needed to make a high quality display, but suffered from low
brightness and very high power consumption. However, a series of advances led to
plasma displays outpacing LCD’s in performance improvements, starting with Fujitsu's
improved construction techniques in 1979, Hitachi's improved phosphors in 1984, and
AT&T’s elimination of the black areas between the sub-
It was the slow standardization of high definition television that first produced
a market for new television technologies. In particular, the wider 16:9 aspect ratio
of the new material was difficult to build using CRTs; ideally a CRT should be perfectly
circular in order to best contain its internal vacuum, and as the aspect ratio becomes
more rectangular it becomes more difficult to make the tubes. At the same time, the
much higher resolutions these new formats offered were lost at smaller screen sizes,
so CRTs faced the twin problems of becoming larger and more rectangular at the same
time. LCD’s of the era were still not able to cope with fast-
Through the halting introduction of HDTV in the mid-
This situation changed rapidly. Contrary to early optimism, plasma displays never
saw the massive economies of scale that were expected, and remained expensive. Meanwhile,
LCD technologies like Overdrive started to address their ability to work at television
speeds. Initially produced at smaller sizes, fitting into the low-
Although plasmas continued to hold an arguable picture quality edge over LCD’s, and even a price advantage for sets at the critical 42" size and larger, LCD prices started falling rapidly in 2006 while their screen sizes were increasing at a similarly furious rate. By late 2006, several vendors were offering 42" LCD’s, albeit at a price premium, encroaching on plasma's only stronghold. More critically, LCD’s offer higher resolutions and true 1080p support, while plasmas were stuck at 720p, which made up for the price difference.
Predictions that prices for LCD’s would drop rapidly through 2007 led to a "wait
and see" attitude in the market, and sales of all large-
When the sales figures for the 2007 Christmas season were finally tallied, pundits
were surprised to find that LCD’s had not only outsold plasma, but also outsold CRTs
during the same period. This evolution drove competing large-
LCD's dominance in the television market accelerated rapidly. It was the only technology
that could scale both up and down in size, covering both the high-
* In October 2004, Sharp announced the successful manufacture of a 65" panel.
* In March 2005, Samsung announced an 82" LCD panel.
* In August 2006, LG Display Consumer Electronics announced a 100" LCD television
* In January 2007, Sharp displayed a 108" LCD panel under the AQUOS brand name at CES in Las Vegas.