You’re walking through your local electronics store looking for a new TV and you come across a thing called an “LED TV”. Which then leads you to ask: “Is that the same technology they use for the giant screens at football games?” And the answer, quite simply, is no.
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, “LED” TVs are actually LCDs. That’s right, they’re not LED TVs at all. These so-called LED TVs use a series of LEDs to light up the panel. 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 source because it emits no light of its own.
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). CCFL used to be the most widespread method of backlighting for LCD televisions, and consists of a series of tubes laid horizontally down the screen.
LED backlighting is now very common and 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.
Backlit (full array) or edgelit?
There are two different methods of LED backlighting: Backlit and edgelit. The main advantage of backlit is that it can be used to increase contrast levels by turning selected LEDs off through a function known as local dimming–thus increasing the amount of black in parts of the picture.
In comparison, edgelit’s main advantage is that it can be used to make TVs that are incredibly thin–the LEDs are at the side and not behind the panel. Local dimming is now available for edgelit TVs, too, but with much fewer “dimmable” segments compared with its backlit counterpart: Tens versus hundreds.
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 TV 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.
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. However, it has been some time since a TV manufacturer launched an RGB LED TV. The last model was the 2009 Sharp LC-65XS1M.
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. Two LED modules are deployed along the 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 finer backlight control compared with its predecessor. To put this into perspective, an LED-backlit 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.