LCD panels explained
With all the complex technologies that help make flat panel monitors and flat-screen televisions, well, flat, it's no surprise there's some confusion about exactly what's happening behind our favorite screens.
If you're in the market for a new TV or monitor, it's helpful to know what all the acronyms and spec-speak actually means for your viewing and using experience. Maybe you already appreciate the price differences between LED Full Array and LED Direct Lit TVs, but once you know how these configurations really work, you'll really start seeing their value in a completely different light.
There's a lot of confusion and misconceptions about the science of panels, so this display explainer aims to give a basic breakdown of the types of displays available today. It's our hope that by the end of our two-page primer you'll be officially certified to school friends and family in screen tech 101. Plus, when it's time to go shopping for a new TV or monitor, you'll be fully informed as to what you're buying.
One last note on resolution before we get started: All the panels listed - with the exception of plasma - can produce a 4K picture, but nowadays most screens typically come at resolutions of 1920 x 1080, though it's not a hard and fast rule.
Now that we have that cleared up, let's start with the basics: LCDs.
LCD and Light Polarization
It's no surprise that one of the oldest flat-panel technologies is also the one with the most variant off-shoots. But to understand liquid crystal displays (LCD) you have to first wrap your head around the concept of light polarization.
Polarizing light works like a filter to block and isolate specific light waves. This is why polarized sunglasses are popular, since they block out sunlight through super tiny slits that essentially stops light in its tracks.
In simple terms, light waves travel vertically and horizontally, and polarized glass uses the slits to block out one of these waves at any given time.
When that specific light wave passes through the glass, it can only pass through polarized glass if it is in the same orientation (horizontal or vertical) as the glass. Layers within LCD displays are oriented to let in one of these types of light waves.
LCD variations - TN, VA, IPS and PLS explained
There are several kinds of LCD displays found in today's TVs and monitors. The distinction is often not spelled out clearly on a spec sheet, but knowing what kind of display you're shopping for can make for smarter purchasing decisions.
TN - Stands for Twisted Nematic, which is one of the most common types of LCDs. Its application in consumer devices use dates back to the late 1960s and traditional TN displays can still be found today in calculators, alarm clocks and budget media players. In other words, most consumer electronics you can find in a drug store.
LCD is comprised of a material known as nematic liquid crystal, which is the substance that's placed between plates of polarized glass.
It gets its name from the liquid crystal's reaction to an electric field. The absence of such a field twists the cell 90 degrees. Conversely, the presence of an electric field (after voltage is applied to the electrodes) forces the liquid crystal molecules to align with the field.
In layman's terms that means the presence of electrical current allows light to pass through, while the lack of current means the pixel stays dark.
How you can explain it to mom: Light travels one of two ways: horizontally and vertically. TN technology works as a kind of "light dam" that controls when light does and does not pass, and whether you have a lit pixel or a pixel devoid of light on your screen. Twisted nematic literally twists its light filter horizontally or vertically to block light or to let it go through.
Devices you find it in: Digital watches, calculators, car instrument panel displays, first-generation flat-panel computer monitors as well as various monitors today.
VA - Stands for Vertical Alignment. It's often considered the middle child of the group between TN panels and IPS displays.
Like Twisted Nematic panels, Vertical Alignment panels use liquid crystals and electrical current to tilt polarized glass but have a slightly altered manufacturing process. The result is a deeper black background, better image quality, and a higher contrast ratio over traditional twisted nematic displays.
As a group, vertically aligned liquid crystal molecules are more organized than TN molecules, which are neither fully vertical nor horizontal. This results in better control of light and less light leakage in VA displays. If you like great viewing angles and dark blacks, and don't mind average response time, VA monitors are fine options.
How you can explain it to mom: VA monitors are better than TN panels, but still not the best LCD screen you can get.
Devices you find it in: Computer monitors. You'll find them next to IPS and TN displays at the electronic store.
IPS - Short for In-Plane Switching, IPS was primarily designed to solve TN's limitations, including limited viewing angles and color reproduction.
Whereas TN liquid crystals slide around the panels of glass, IPS liquid crystals are kept in place using an electrical field. To generate this field, IPS panels need twice as much electricity to power the increased number of transistors. As a result, IPS displays consume more power than TN displays.
Like Vertical Alignment, In-Plane Switching controls liquid crystal molecules better than Twisted Nematic. To be "in-plane" also means to be parallel with the glass outer layers, which leads to more focused light.
How you can explain it to mom: IPS panels have the best color reproduction of any standard LCD display. The contrast isn't as good as LCD LED displays, but IPS panels are usually cheaper.
Devices you find it in: Computer monitors, competing with VA and TN displays.
PLS - Plane-to-Line Switching technically falls under the IPS classification. The only notable difference is that PLS is manufactured exclusively by Samsung, which claims that PLS is more cost-efficient to produce than IPS.
With similar response times and contrast ratios, PLS is generally considered similar in nature to IPS, just manufactured by one company.
That's not to say it's only found in Samsung monitors, though. Samsung makes PLS panels for other device manufacturers like Dell, AOC and even Philips.
How you can explain it to mom: PLS is a tweaked version of IPS branded by Samsung.
Devices you find it in: Primarily Samsung computer monitors, although Dell, AOC, and Philips buy PLS panels from Samsung for their screens as well.
LED and Plasma displays explained
It was just a couple years ago that television manufacturers started selling LCD TVs alongside LED TVs, leading to complete and utter confusion for everyone involved.
Technically, LED TVs are LCD TVs, but they use an improved light source compared to older flat panel televisions. Older LCD TVs relied on cold cathode fluorescent lamps (CCLFs), which operate based on two phenomena: electron discharge and fluorescence, while LEDs use - you guessed it - light-emitting diodes.
Don't freak out. While the technology sounds like something only Tesla himself could understand, it's quite accessible once you wrap your head around it.
Shedding a light on LED
Ask any tech lover worth their weight in silicon and they'll tell you that LED stands for light-emitting diodes, which are smaller and more energy efficient than CCFLs.
LED TV's most marketable feature has been improved backlighting, but the picture quality remains unchanged compared to CCFL-based LCD televisions. Even though LED TVs have gotten less expensive over the years, home theater stores have been using the LED term more often than LCD, as it leaves buyers feeling like they're getting a newer product.
LED backlight technology functions under one of three configurations:
Full Array: A high-end configuration of LED, full array panels distribute the diodes evenly across the screen. Having this uniform backlight allows for more accurate local dimming, where changes in luminosity only occur in a specific part of the screen.
Edge Lit: Instead of placing diodes throughout the screen, edge lit panels have bulbs along its outside edges. While this version is cheaper to produce than Full Array, the unbalanced configuration often results in an uneven spread of brightness, where the edges are brighter than the rest of the screen.
Direct Lit: Direct lit screens function a lot like a budget version of Full Array. Direct Lit has a spread of diodes across the screen, but uses much fewer LEDs than Full Array. Moreover, these lights cannot be controlled separately to match a given picture's luminosity.
Devices you find it in: The television market is currently dominated by LED with Sony, Panasonic, Samsung, LG and others all producing TVs with the tech. Some retailers are better than others in denoting whether a given TV features Full Array, Edge Lit or Direct Lit lighting, so be sure to do some research before buying.
LED vs OLED
Keeping in mind that LED is essentially souped-up LCD, LED panels have gone one step further in the race for screen supremacy by trading out the filament in the bulb for a brighter, better organic substance in a technology called OLED.
OLED technology is impressive in that it allows for ultra-thin, high-performance monitors. How does it do it? OLED accomplishes this with a six-layer design structure comprised of protective glass or plastic on both sides, positive and negative terminals, and a pair of layers of organic molecules in the middle.
The layer with the organic molecules' interaction with the cathode are what produce the light, while color is created using filters beneath either the top or bottom layer in conjunction with photons. Combined with thousands of red, blue and green OLEDs, these diodes work similarly to LCDs as each color is switched on and off independently.
Due to its thinner display, improved color reproduction, and greater brightness, OLED is often considered a step up over LCD technology. It would be adopted more widely if not for its current shortcomings, which include degradation of the organic molecules, sensitivity to water and steep price tag.
How you can explain it to mom: It isn't perfect, but OLED panels are the best of the best right now. Each pixel is individually lit and therefore has impossible-to-see levels of contrast.
Devices you find it in: High-end televisions including curved TVs and 4K TVs like the LG 65EC9700 and Samsung's S9C series.
There's also AMOLED, which stands for "active-matrix organic light-emitting diode." It's a modified version of OLED where semiconducting film is added behind the panel. The result is a quicker response time for each pixel.
AMOLED screens also benefit from a superb color spectrum as well as great contrast, which is why this technology is primarily used in smartphones and tablets. Their wide viewing angles also make them suited for curved handsets, like the Samsung Galaxy S6 Edge.
How you can explain it to mom: Whereas the pixels in OLED react to a single power source, each pixel in an AMOLED display has its own individual power source.
Devices you find it in: Media players, smartphones, and digital cameras. You won't find AMOLED in TVs or monitors, but since it's a variation of OLED we determined it warranted inclusion in this explainer.
Understanding plasma before it goes extinct
Plasma is created when electrons are generated in gas as a result of high heat. For the purposes of TVs and monitors, plasma is contained in glass spheres as filtered light passes through them from microscopic lamps.
This results in excellent black levels, one of the reasons why plasma has its share of enthusiasts, but risks of image burn-in and high energy consumption limited plasma's wider adoption. Furthermore, OLED has since outmatched plasma in terms of black levels, contrast ratio and color accuracy. Given that manufacturers have ceased production of plasma televisions, 2015 will most likely be the last year you can find plasma TVs in major retailers.
How you can explain it to mom: In high heat, gas gives off electrons. Electrons light up microscopic bulbs of red, blue and green pixels and we see an ultra sharp picture.
Devices you find it in: A very select number of Samsung and LG televisions. Don't expect new plasma TV models in 2016.
If you're interested in learning more about the future of resolutions, check out our 4K and UHD primer. This screen tech is still some time away from going mainstream thanks to its extremely high price points, but we will see more and more 4K-and-beyond screen tech in the years to come.
April 30, 2015 at 02:45AM
Miguel Concepcion and Nick Pino
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