Starting or upgrading a home theater setup can involve a lot of different things, but it often comes down to one major question: What kind of TV should you get? Flashy TVs like OLED models from LG or Sony or Samsung’s QLED TVs might get a lot of press, but most of us have budget constraints that limit our options, bringing two terms up again and again: LED and LCD.
But what’s the difference? It’s a question we hear a lot from budding home theater shoppers, but we really shouldn’t. We blame the acronyms. Here’s the quick answer: An LED TV is an LCD TV, but how the definition of each term became so muddled might come as a surprise.
LED and LCD: Together forever
Despite having a different acronym, an LED TV is just a specific 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 TVs.
An LED TV uses 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. 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.
Since both LED and LCD TVs are based around LCD technology, you’re probably wondering what the difference is. Actually, it’s about what the difference was. Older LCD TVs used cold cathode fluorescent lamps (CCFLs) to provide backlighting, whereas LED-backlit LCD TVs used an array of smaller, more efficient light-emitting diodes (LEDs) to illuminate the screen. As the technology is better, all LCD TVs now use LED lights and are colloquially considered LED TVs. For those interested, we’ll go deeper into backlighting below, or you can move onto the Local Dimming section.
There are three basic forms of illumination that have been used in LCD TVs: CCFL backlighting, full-array LED backlighting and LED edge lighting. Each of these illumination technologies is different from one another in important ways. Let’s dig into each.
CCFL backlighting is an older, now-abandoned form of display technology in which a series of CCFLs sit across the inside of the TV behind the LCD display. The lights illuminate the crystals fairly evenly, which means all regions of the picture will have similar brightness levels. This affects some aspects of picture quality, which we discuss in more detail below. Since CCFLs are larger than LED arrays, CCFL LCD TVs are thicker than LED-backlit LCD TVs.
Full-array backlighting swaps the outdated CCFLs for an array of LEDs spanning the back of the LCD screen, comprising zones of LEDs that can be lit or dimmed in a process called local dimming. TVs using full-array LED backlighting make up a healthy chunk of the high-end TV market, and with good reason — with more precise and even illumination, they can create better picture quality than CCFL LCD TVs were ever able to achieve, with higher efficiency to boot.
Another form of LCD screen illumination is LED edge lighting. As the name implies, edge-lit TVs have LEDs along the edges of a screen. There are a few different such configurations, including LEDs along just the bottom, LEDs on the top and bottom, LEDs left and right, and LEDs along all four edges. These different configurations result in differences in picture quality, but the overall brightness capabilities still exceed what CCFL LCD TVs could achieve. While there are some drawbacks to edge lighting when compared to full-array or direct backlight displays, the upshot is edge lighting allows for manufacturers to make thinner TVs which cost less to manufacture.
To better close the local-dimming quality gap between edge-lit TVs and full-array backlit TVs, manufacturers like Sony and Samsung developed their own advanced forms of edge lighting. Sony’s technology is known as “Slim Backlight Master Drive,” while Samsung has “Infinite Array” employed in its line of QLED TVs. These keep the slim form factor achievable through edge-lit design but with local dimming quality more on par with full-array backlighting.
What is local dimming?
Local dimming is a feature of LED LCD TVs wherein the LED light source behind the LCD is dimmed and illuminated to match what the picture demands. LCDs can’t completely prevent light from passing through, even during dark scenes, so dimming the light source itself aids in creating deeper blacks and more impressive contrast in the picture. This is accomplished by selectively dimming the LEDs when that particular part of the picture — or region — is intended to be dark.
Local dimming helps LED/LCD TVs more closely match the quality of older Plasma displays (RIP) and new OLED displays, which feature better contrast levels by their nature — something CCFL LCD TVs couldn’t do. The quality of local dimming varies depending on which type of backlighting your LCD uses, how many individual zones of backlighting are employed, and the quality of the processing. Here’s an overview of how effective local dimming is on each type of LCD TV.
Full-array and direct local backlighting
TVs with full-array backlighting have the most accurate local dimming and therefore tend to offer the best contrast. Since an array of LEDs spans the entire LCD screen, regions can generally be dimmed with more finesse than on edge-lit TVs, and brightness tends to be more uniform across the entire screen. Vizio’s impressive P-Series and M-Series TVs are great examples of relatively affordable models that use multiple-zone, full-array backlighting with local dimming.
“Direct local dimming” is essentially the same thing as full-array dimming, just with fewer LEDs that are spread further apart in the array. It’s worth noting, however, that many manufacturers do not differentiate “direct local dimming” from full-array dimming as two separate forms of local dimming. We still feel it’s important to note the difference, as fewer, further-spaced LEDs will not have the same accuracy and consistency as full-array displays.
Because edge lighting employs LEDs positioned on the edge or edges of the screen to project light across the back of the LCD screen, as opposed to coming from directly behind it, it can result in very subtle blocks or bands of lighter pixels within or around areas that should be dark. As such, the local dimming of edge-lit TVs can sometimes result in some murkiness in dark areas when compared with full-array LED TVs. It should also be noted that not all LED edge-lit TVs offer dimming, which is why it is not uncommon to see glowing strips of light at the edges of a TV and less brightness toward the center of the screen.
Since CCFL backlit TVs do not use LEDs, models with this style of lighting do not have dimming abilities. Instead, the LCD panel of CCFL LCDs is constantly and evenly illuminated, which makes a noticeable difference in picture quality compared to LED LCDs. This is especially noticeable in scenes with high contrast, as the dark portions of the picture may appear too bright or washed out. When watching in a well-lit room it’s easier to ignore or miss the difference, but in a dark room, it will be, well, glaring.
OLED vs QLED
As if it wasn’t already confusing enough, once you begin exploring the world of modern display technology, new acronyms crop up. The two you’ll most commonly find — and the two most important — are OLED and QLED.
Despite the similar sounding name, OLED (Organic light-emitting diode) TVs are in a category all their own. We have an in-depth guide as to the differences between OLED and QLED displays, but here’s a quick overview: OLED displays utilize a panel of pixel-sized organic compounds that respond to electricity. Since each tiny pixel –millions of which are present in modern displays — can be turned off individually, OLED displays offer incredibly deep contrast ratios and better per-pixel accuracy in the picture than any other display type on the market. OLED displays are often found on high-end TVs in place of LEDs, but that doesn’t mean that LEDs aren’t without their own premium technology.
QLED is a premium tier of LED/LCD TVs from Samsung. Unlike OLED displays, QLED is not a so-called emissive display technology. However QLED TVs feature an updated illumination technology over regular LED LCDs in the form of Quantum Dot material (hence the “Q” in QLED), which raises overall efficiency and brightness. This translates to better, brighter grayscale and color, and enhances the HDR (High Dynamic Range) abilities.
For a more detailed explanation of QLED be sure to read our list of the best TVs you can buy, which details the many features of QLED and OLED TVs. We also recommend checking out our OLED vs. QLED piece for a look at how these two premium-tier display technologies stack up. And for a look into the future, check out our OLED vs MicroLED guide to bone up on the TVs of the near future.