Battle of TV's Biggest Brands
It's starting to look like LED isn't good enough anymore. The term (an abbreviation for light-emitting diodes) describes a now-standard method of lighting LCD televisions, to the point that most LCD TVs are now called LED TVs. In order to stand out, LG and Samsung have added letters to the term to carve out specific labels for their own high-end TVs. LG's flagship TVs are OLED, while Samsung calls its top-end models QLED. They look and sound similar, but they're very different technologies.
Before we get into what makes them different, it's important to understand what LED means. LED-backlit LCD TVs consist of two main parts: the panel and the backlight. The panel is an LCD (short for liquid crystal display) sheet that can produce images when electricity flows through it. The LCD generates the individual pixels of the TV, activating different combinations of red, green, and blue sub-pixels to produce the correct color for each pixel.
LCDs don't produce light, and without a backlight the pictures they form would be very difficult to see under most lighting conditions. That's why LCD panels need to be backlit by separate light sources either behind or along the edges of the panel. On early LCD TVs, these lights were bulky cold-cathode fluorescent lamps (CCFLs), but in the past few years thinner, lighter, and more energy-efficient LED lighting systems have all but completely replaced them.
At their simplest, LED backlights just illuminate the LCD panel so you can see the picture it's displaying. More advanced TVs use arrays of dimmable LEDs to make parts of the TV brighter or darker, improving the contrast of the picture. The more individually controllable LEDs in the array, the more the backlight can improve the TV's contrast ratio and prevent halos and auras in the shadowy parts of high-contrast scenes.
LG and OLED
Organic light-emitting diode, or OLED, TVs sound like they should be very similar to LED TVs. After all, the letters are there, and they even mean the same thing. The logical conclusion from the term would be that OLEDs are just LEDs that have an organic component to them. That's true in the most basic sense, but OLED displays are actually wildly different from LED-backlit LCD TVs.
OLED TVs use panels of OLEDs to both generate and illuminate the picture. Each pixel on an OLED panel is produced entirely by the OLEDs themselves, determining the color of that pixel and causing it to produce light. Mechanically, OLED displays are much closer to now-defunct plasma TVs, which consist of individual plasma cells coated with colored phosphors, determining both the color and the light of each pixel on a single panel. The chemistry, engineering, and physics of the two technologies are wildly different, but fundamentally they do the same thing: generate a picture that doesn't require an external light source for illumination.
Because each pixel generates its own light, OLED panels can produce the best possible contrast of all display technologies. If part of the picture is black, those pixels can simply turn off and emit no light at all. This is a stark difference from LED lighting arrays for LCD panels, which always bleed some form of light to parts of the panel that should be unlit. Excellent LED TVs generate less than 0.01cd/m2 of light for black sections of the screen. OLED TVs produce no light at all for those same sections. This is why OLED TVs are often described as having "infinite" contrast—no matter how bright the screen can get, the black level is always zero.
See How We Test TVs
OLED panels are very expensive to manufacture in large sizes, so OLED TVs are consistently pricey to match. This is why LG keeps OLED technology reserved for its very high-end TV models. The "entry-level" (and Editors' Choice) 55-inch OLED55B6P retails for $2,299. The 65-inch LG Signature OLED65W7P, meanwhile, costs $7,999. This is why LG is one of the few major TV manufacturers to offer OLED TVs, though Sony also has a few OLED models available.
While LG is the biggest name for OLED TVs, OLED technology is much more common in smaller form factors. OLED displays are used in many high-end mobile devices, including Samsung's own Galaxy S8 phones. OLED panels are consistently more expensive than LCDs, but the cost decreases significantly as panel sizes scale down.
Samsung's QLED
Samsung's flagship QLED TVs are, according to the company, comparable with OLED TVs. The terms even look similar, just with a little line coming out of the O to turn it into a Q. However, while Samsung QLED TVs might have very advanced technology in them, they're still fundamentally LED-backlit LCD televisions.
QLED TVs use LCD panels and LED backlight arrays, like many high-end LED TVs. The QLED descriptor is a Samsung marketing term that indicates several Samsung-specific enhancements to the TVs. To start, QLED TVs use Samsung's Quantum Dots technology for its LCD panels. Quantum Dots are nanoparticles that emit or alter light at different frequencies when exposed to electricity. This light-tweaking can produce more precise color in a wider range than the LCDs illuminated by white LEDs can.
A wider color gamut is very beneficial, but as an LED-lit LCD panel, QLED TV contrast is still a big concern—the technology doesn't appear to produce the perfect black levels that OLED panels can. To improve contrast, QLED TVs are treated with a low-reflectivity finish while producing a peak luminance of 1,500 to 2,000cd/m2 according to Samsung. We'll confirm whether or not QLED TVs can offer that sort of performance when we get them in the lab for full review.
QLED TVs are as pricey as LG's OLED TVs, with the least expensive model, Samsung's 55-inch Q7F, retailing for $2,799. The price and size ceiling for QLED TVs stands at $9,999, for the 75-inch Q9F.
For now, you should simply understand that QLED is not the same as or similar to OLED. It might make an excellent picture as well, but the two technologies are as far apart from each other as OLED and conventional LED-lit LCD TVs.
Big Features for Both
Since OLED and QLED are technologies for flagship televisions, OLED and QLED TVs are equipped with all of the features expected of top-end models. Specifically, both TV types have 4K resolution and support HDR content.
Ultra high-defiinition (UHD, or 4K) is the new standard for consumer television resolution. 4K TVs are 3,840 by 2,160, displaying four times as many pixels as 1080p TVs. Most major TV manufacturers have all but replaced their 1080p TVs with 4K models, with the exceptions of some low-end budget TVs. If you buy a new, brand name TV larger than 40 inches this year, it will likely be 4K.
High dynamic range (HDR) is a series of video standards that let TVs display a wider range of color and light than standard dynamic range video. HDR video comes in two major standards, HDR10 and Dolby Vision, with a few new standards and variants coming out recently. HDR10 is the format used with Ultra HD Blu-ray discs, and both LG OLED and Samsung QLED TVs can display them. While Samsung TVs don't support Dolby Vision, most streaming services that offer HDR content in Dolby Vision also support HDR10, and Samsung recently announced a new HDR10+ standard it will be implementing with Amazon Video.
Of course, both types of TVs are also fully connected, smart TVs that support streaming video services and apps. LG smart TVs use WebOS, while Samsung TVs use the company's Smart Hub interface. Both are connected platforms developed internally by their respective manufacturers, and both support all major 4K, HDR streaming services.