LED vs. LCD TV: Which is better?
While the giant display in a sports stadium, for example, is made up of thousands of LEDs that are used to directly produce a picture, Samsung's "LED" TVs are actually LCDs. That's right, they're not LED TVs at all. Confused?
Samsung's televisions use a series of LEDs to light up the panel from the rear, and it's not the only company that does this. But what is backlighting anyway?
Why do LCD screens need a backlight?
As a consumer technology, LCD has been in widespread use since the early 1970s when it first appeared in digital watches. As its name suggests, Liquid Crystal Display is a liquid which has been sandwiched between two plates, and it changes when a current is applied to it.While we've had black-and-white LCDs for years, color LCDs are a lot more recent, but the technology is the same. As we all know, you need to press a button to read a watch in the dark, and an LCD TV is no different. It needs a light behind it because it emits no light of its own.
A selection of LCD screens, including Samsung's 6 and 7 series, showing the differences between backlighting technologies. The panel on the right features a fluorescent tube backlight.
(Credit: CNET Asia)
What types of backlights are there?
At present there are two main methods of backlighting in LCD flat panels: Cold-Cathode Fluorescent Lamp (CCFL) and LED (light-emitting diode). There are several others, and these includes Sony's Hot Cathode Fluorescent Lamp (HCFL), though only one television currently uses this technology.CCFL is the most widespread method of backlighting for LCD televisions, and consists of a series of tubes laid horizontally down the screen.
A cutaway of a CCFL-backlit LCD showing the different layers of polarizers and filters, and the thin fluorescent tubes themselves on the right.
(Credit: Ty Pendlebury/CNET Australia)
LED backlighting is still relatively rare, but has been in use in televisions since 2004 when it first appeared on a Sony WEGA television. Though there are several different ways of backlighting using LEDs (as we'll explain shortly), the idea is the same: A lot of LED bulbs are used to light the screen.
Direct- or edge-mounted?
There are two different methods of LED backlighting: Direct and edge. The main advantage of direct lighting is that it can be used to increase contrast levels by turning selected LEDs off--thus increasing the amount of black in parts of the picture. LG is one of the champions of direct lighting.In comparison, edge lighting's main advantage is that it can be used to make screens that are incredibly thin--the LEDs are at the side and not behind the panel. Of course, you lose the ability to switch off parts of the backlighting for better contrast, and picture quality could also suffer if light isn't sufficiently well dispersed.
White or RGB light?
White LED is very similar to CCFL because LED uses a blue light source that is made to look white by the presence of a sulphur coating on the bulb. As a result, the television will potentially be stronger in the green portion of the spectrum. But as some CCFL technologies enable better red and blue response, better white LEDs could also be possible. The Samsung UA40B7100 is an example of a TV that uses white LEDs.
An edge-mounted, white LED module.
(Credit: Ty Pendlebury/CNET Australia)
RGB LEDs, on the other hand, are potentially capable of a broader color range because they use three LEDs colored red, blue and green. Its proponents argue that there is less of a green "push" as a result and the color spectrum is more evenly distributed. The Sony Bravia KDL-46X4500 is an example of a television that uses RGB LEDs in its backlight.
An RGB backlight.
(Credit: Samsung)
Samsung's technology under the microscope
The Korean company's LED-edgelit unit comprises two major components: A long LED module with a row of tiny white diodes and a thin screen-sized plastic sheet known as a light guide plate. Four LED modules are deployed along the left, right, top and bottom of the panel. The combined light output is then funneled and redistributed evenly across the screen.Essentially, the edgelit LED system lacks fine backlight control compared with its predecessor. To put this into perspective, a Samsung series 9 panel can turn on selected LEDs to bring out the sparkle of stars in a galaxy while switching off the remaining bulbs to produce deep blacks for the background. In the case of the new LED TVs, the lumens are set at screen level, so there's a contrast tradeoff when rendering scenes with both bright and dark portions.
Samsung's edgelit screen requires a light guide plate, which is used to distribute light across the panel.
(Credit: CNET Asia)
Is the price premium for LED worth paying?
We find it interesting that TV manufacturers are currently demanding a higher asking price for LED backlighting when many cheap devices--particularly mobile phones and Netbooks--use LEDs as backlights. According to Samsung, LED backlights currently cost three times more in large sizes than the equivalent CCFL arrangement, and this is mostly due to a smaller number of manufacturers. Presumably, when the technology begins to take a firmer hold, the price will come down due to increased competition.The few LED-backlit screens we've seen have been very good, and while we personally prefer plasma, the combination of thin design and sharp picture quality will find favor with many people. If you're looking for a further explanation of how LCD screens work, check out this video on the 3M site.
The original story first appeared in CNET.com.au
Latest comments
lcdguru's insite is nothing but a bunch of technical babble and unfortunately not all true. Go to your local electronics store and compare the new LED LCD's to the other LCD's with CCFL. There is an unarguably better picture quality and clarity with the new backlit tv's. You really think users are going to be breaking into their tv's wondering if the whiting is at the perfect grade...lmao. Leave that to the manufacturing specialists. Like JahMekYah said above, let the end decide...go see for yourself. Don't fully rely on one persons opinionated review. I have an LED and I love it!
Wow...This is really embarrassing for Cnetasia! lcdguru shed more light on Cnet's own article. Thanks lcdguru I'm definitely not going to pay more for a LED TV! Manufacturers misleading consumers, what else is new?! Damn!
Thanks lcdguru. To be honest,I am hoping Cnetasia can produce more insightful write-ups like yours. It was a little frustrating see regurgitation of the facts without shedding more light on the issue for the reader. And yup, JahMekYah. A title is a title. Still, peace to all and merry xmas!
All said and done, the term LED TV is a misnomer and the average consumer is easily misled into thinking that it is some new technology that promises quantum leaps in clarity, contrast, vividness of colors, great viewing angles etc. Color TV is a mature industry in a marketplace that is becoming ever more crowded - with new upstarts jostling for standing place with old timers and not-so-old timers. Profits for TV manufacturers have become razor-thin and, even negative for some. Hence the sheer desperation to find something to attract consumer interest -- even deploying the occasional hoodwinking via misleading information. After all who cares if the consumer finds out that his newly acquired "cutting-edge tech" LED TV is indeed the old LCD TV with a backlight that is lit by a bar of white LEDs instead of the usual CCFL ? The important thing is : the manufacturer has succeeded in persuading the consumer to part with his money - mission accomplished. In reality, an "LED" TV may not always be superior to a conventional CCFL backlit LCD TV. Unknown to most people outside of the industry, it is extremely difficult to make consistent LEDs in white. There is a huge range of fluctuation in terms of brightness and color tinge in any production batch of white LEDs. Though there is a standard sorting procedure used by LED mfrs to grade brightness and color tinge (called variation in color coordinates), in reality every LED in the backlight array is different. Out of 100,000 TVs made, perhaps there is only one or two that would have the perfect LED backlight. From one end of the TV screen to the other, there will be bound to be variations in brightness and color tinge. And the brightness variation problem will get worse as time goes on, because as lower grade LEDs in the array are driven harder to compensate for their inherent lower brightness, their lives get shorter than the higher grade ones. Even this leads to uneven brightness across the screen. In any batch of production of white LEDs, the range of so-called acceptable grades is really small, no more than 50% at best. This often leads to a supply crunch, as the other TFT LCD applications such as mobile phones and increasingly, monitor screens and notebook pcs, compete for white LED supplies. When push comes to shove, inevitably, TV manufacturers will have to compromise and start widening their "acceptable range" of grades. This eventually appears as less-than-satisfactory displays in the TVs. It is claimed that "LED TVs" have higher NTSC color gamut, but this is again doubtful unless the display screen under test has that perfect backlight. Also, the color filters on the TFT LCD that makes up the screen are still the predominant factor in rendering color vividness. So dont be taken in so fast yet. Apparently the main advantage with LED backlighting appears to be that it is more "green" and thus more environmental-friendly than the CCFL type. There are hazardous materials used inside the CFFL coatings and the mercury vapor that fills CCFL is also poisonous. Plus CCFL needs special electronic circuits called invertors to get them to light up. However, for the whole equation to be considered valid, one needs to evaluate the production of white LEDs in detail. They still need a special fluorescent coating that converts the original blue light from the LED dice into white, plus special white LED driver ICs are needed to drive the finished LEDs. Time will tell all if it is all that green. Talking about mobile phones, everyone of them has an LED backlight, strangely nobody calls them LED displays or LED phones ! www.crystalimage-lcd.com www.dogsbed.biz
Even if the author answers the title, its still his opinion and only end user who uses both can say which is. A title is a TITLE
hmmn.. it should be titled: LED Explained
does the author need to answer the question he poses? think about it yourself!
Read your title. Did you answer the question?
Join the conversation
Sign In with Facebook or create an account to post a review.
