LED and LCD – what’s the difference? It’s a question we hear a lot from budding home theater shoppers. Blame the acronyms. While yesterday’s consumers had to make a simple choice between CRT and rear-projection television sets, today’s consumers are confronted with plasma, LCD, DLP, OLED, and laser televisions. And now, the age-old term LED has been stirred into the mix. Let’s take a look at what those three magic letters mean, how they apply to televisions, and why you might want to consider buying one.
An LED TV is an LCD TV
Despite having a different acronym, an LED TV is just a different type of LCD TV. The proper name would actually be “LED-backlit LCD TV,” but that’s too much of a mouthful for everyday conversation, so people generally just refer to them as LED TV’s, which can cause confusion.
Both types of TV make use of a liquid crystal display (LCD) panel to control where light is displayed on your screen. These panels are typically composed of two sheets of polarizing material with a liquid crystal solution between them, so when an electric current passes through the liquid, it causes the crystals to align so that light can (or can’t) pass through. Think of each crystal as a shutter, either allowing light to pass through or blocking it out.
Now, since both LED and LCD TV’s use LCD technology, you’re probably wondering what the difference is. The answer? Backlighting. Ordinary LCD TV’s use cold cathode fluorescent lamps (CCFL’s) to provide backlighting, whereas LED TV’s use an array of smaller, more efficient light emitting diodes (LED’s) to illuminate the screen, which gives them a few advantages.
The benefits of LED backlighting
LED TV’s carry a number of advantages over regular LCD TV’s with CCFL backlighting. First of all, LED’s are considerably smaller than CCFL tubes, which means LED TV’s can be made much thinner. These days, most TV’s that measure under an inch thick are made with LED because they add very little depth to the display profile.
LED’s also consume less power than their CCFL counterparts, but the most important difference between the two is a feature called local dimming – a selective lighting technique that allows for deeper blacks and better overall picture.
The problem with CCFL backlighting is that fluorescent tubes must light the entire screen evenly, so designers have no way to vary the backlighting intensity in different parts of the screen. Even if you want to show a single white pixel on an all-black screen, the light in the back needs to be blazing away at full brightness. LED TV’s offer a solution to this with local dimming. The idea behind this technique is to control the output of the LEDs so that, rather than be on at full brightness all the time, they can be dimmed or turned off entirely.
This makes for much better black levels and contrast. Think of a space scene. You’ve got this big pool of black, interrupted by little dots of brightness (stars) and maybe one bright object (perhaps a planet or spaceship) in the middle. This is an extremely difficult image to pull off well because LCD panels aren’t that great at blocking out all of the light coming from the backlights. That’s where local dimming can come in handy. With this feature, the TV can shut off all the lights it doesn’t need and just use the right ones to make the stars and spaceship nice and bright.
However, it should be noted that not all LED TV’s come equipped with local dimming. Broadly speaking, LED TV’s come in two varieties: edge-lit and full-array, and only full-array TV’s can pull off local dimming well enough to compete with plasma TVs on a respectable level. Recently, some manufacturers have developed edge-lit televisions with local dimming functionality (Samsung UND8000 series; LG LW5600 series), but due to the way they’re built, they generally can’t “turn off” different parts of the screen intelligently the same way a full-array set can. When buying an LED TV, make sure you know whether it’s edge-lit or full-array before you pull out your wallet.
Efficient, bright, and stylish – but economical?
What does all this mean for the befuddled TV buyer? Well, if you can afford one, an LED-backlit HDTV is the way to go. These badboys are thin, easy to mount, energy efficient, and can produce a great picture – but all these benefits come at a premium. If you’re on a budget but you still want a great picture, look for a good plasma screen. They’re power hungry and usually a bit on the bulky side, but offer a cinematic experience similar to what you’ll get on an LED TV, and for not nearly as much money. CCFL backlit LCD TV’s are going the way of the Dodo, but might be the only option if you’re working with a limited budget.
Header LED image via Shutterstock