This is the second installment in our series on TV terminology intended to cut through the smoke and mirrors swirling around today’s TV market. The more you know, the more likely you’ll wind up with the best TV for the buck.
The first story in this series covers screen size, resolution, and speed, as well as the mission behind this series. We dispel the mysteries of color spaces and standards in part three.
Display technology and types
The following are some basic TV technologies that you should to know about before you even think about shopping for a TV. For more a more granular discussion on LEDs and lighting, read the fourth installment of this series.
3D TV: A TV that is capable of reproducing three-dimensional content. It works its magic via stereoscopy, or displaying slightly different images to each eye to give an illusion of depth. This can be done one of two ways: Passively, by displaying two images at the same time and using eyeglasses that filter different colors to each eye; or actively, by showing two images consecutively and using powered glasses with polarity shutters to blind each eye in turn.
Every 20 years or so, 3D becomes a big deal, then fades away. It’s currently faded, likely due to the glasses and that turning a generally passive experience into an active one wearies users.
Active matrix/passive matrix: The pixels in all flat panel displays are addressed via a matrix of rows and columns. An active matrix uses TFTs (thin film transistors) that use capacitors to actively retain the last state of the pixels. An active matrix responds much quicker than a passive matrix that employs separate substrates to carry the charge and ground it to maintain the “on” state. Passive displays are largely history, and the phrase “Active Matrix” is mostly quoted in sales literature these days because it sounds cool.
Dual-layer LCD: This is Hisense’s term for stacking two LCD layers on top of each other. The rear-most layer is monochrome and currently of lower resolution than the front LCD layer. It augments the backlighting array by greatly reducing light bleed and allowing more granular dimming of areas of the screen. The technology is expected to show up in the U.S. market in 2020.
CCFL (cold cathode fluorescent lamp): The former mainstay LED TV backlight element from just a few years ago. CCFL made for thicker TVs, but it produced a flatter spectrum than the current blue-heavy LED backlighting. Vendors have made great strides in improving color in the last couple of years, but many bargain-priced LED-backlit LCD TVs still suffer the “blues.”
Curved TV: A TV whose surface is slightly concave on the horizontal plane to ostensibly create a sense of immersion, as well as reduce off-angle artifacts—at least when you’re sitting dead center. Some consider it more aesthetically appealing in terms of style—TVs are also furniture, after all—but this design sacrifices some of the depth-saving advantage that modern flat-screen displays deliver. You’ll find more information on curved TVs in this story.
Clear Action: Vizio’s term for strobing the LED backlights in short pulses to reduce motion blur. It’s effective to a point, and many vendors use the same technique.
Edge lighting: Placing a display’s backlight sources at the edge or edges of the screen, and then channeling or distributing the light reflectively across the entire display. This is an older methodology that has been largely supplanted by direct array backlighting on better TVs. Its weakness is bleed and not-so-black blacks.
Full array: An array (grid) of LED backlights spaced evenly, directly behind the other flat-panel display layers (color filters, LCDs, etc.). We have no idea why “array” is preceded by “full;” we’ve never heard of a “partial” array.
Halo, aka blooming: That soft, light haze that you sometimes see when light-colored letters are superimposed on a dark background. This can be, and often is, light bleed from array backlighting; but light passing through the fluid in your eyes causes the same effect to a lesser degree. If you move closer and the phenomena disappears, the cause is the latter.
IPS (in-plane switching): A method of aligning the crystals in an LCD. Unlike twisted nematic (explained below), the crystals are kept parallel (in-plane) to the surface of the display in both their on and off states, allowing light to emit to the sides as well as straight ahead. This makes for wide viewing angles. There are a number of IPS sub-types, including S-IPS, AS-IPS, and IPS Pro, which vary in their effectiveness (listed there from least- to most effective).
QLED: This is not a technology, but Samsung’s branding of their TVs that use quantum dots in front of the LED backlight to improve color.
LCD (liquid crystal diode): A low-power, miniature electronic shutter consisting of crystals suspended in liquid. When power is applied, the crystals realign themselves to let light pass through. The amount of power applied determines the amount of realignment and how much light is let through. Unlike OLEDs and micro-LEDs that produce their own light, LCDs pass through only the red, green, and blue light created by backlighting and the filters placed behind them.
LCD TV: A TV that uses LCD technology. Generally, it will consist of a backlight or backlight array, a light-tunnel, or a similar diffusion layer to evenly distribute the backlighting; a filter layer to change the broad spectrum LED light into red, green, and blue; and the LCDs that block or allow light to pass through according to the requirements of the image.
LED (light-emitting diode): A silicone diode the produces light through electroluminescence; i.e., power applied to a phosphor. For a variety of reasons, but particularly their relatively large size compared to LCDs and larger power draw, LEDs are employed as backlights in TVs rather than as primary display elements. See micro-LED.
LED or array zone: The group of pixels lit by one of an array of LED backlights. The LED for a zone can be dimmed, or even turned off to reduce or eliminate light bleed. This results in darker darks and blacker “black.”
LED TV: Generally, an LCD TV with LED backlighting. (See CCFL) While there are true LED displays, with LEDs that produce both light and color, these are generally used as outdoor signage because of size, power draw, and heat. While not producing the black blacks of an OLED TV, an LED/LCD TV can product substantially more peak brightness (3000 nits compared to 800 or so), and with quantum dots involved, as rich a color palette as an OLED. See micro-LED.
Local, aka, zone dimming: Turning off or dimming the LED backlight/backlights in an array that reside behind an area of a TV that is displaying darker colors. This reduces light bleed and facilitates darker darks. In areas of sharp light/dark contrast, however, local dimming can odd artifacts. .
Micro-LED: Self-emitting pixels which, unlike OLED, use non-organic materials. The technology is currently being offered by Samsung in expensive panels largely used as signage or super large displays. Not to be confused with MiniLED which is a backlighting technology.
Mini-LED: TCL’s term for array backlighiting with thousands of tiny backlights instead of the hundreds that most TVs feature. Not to be confused with micro-LED, which is a self-emitting pixel technology similar to OLED.
Motion blur: While no longer a huge issue with most TVs, this is a phenomena of displays that can’t switch their pixels off quickly enough. As a result, a ghost or remnant of the previous image remains for a short amount of time and creates a blur effect.
OLED (organic light-emitting diode): OLEDs are small, efficient LEDs made from organic compounds that produce both light and color. RGB (three subpixel) OLED pixels are used in computers, mobile device displays, and professional-grade displays, while WRGB OLED pixels (four subpixels, including white to increase brightness) are used in consumer grade TVs. Being self-emitting and not a light source behind a shutter (as LED-backlit LCDs are), OLED suffer no light bleed when in the off state, so they produce an excellent black.
OLED TV: A TV that uses OLEDs to provide both light and color. Though they’ve dropped tremendously in price the last few years, OLED is still an expensive technology due to continuing issues with low production yields (the ratio of saleable to defective panels produced at the factory). The key advantage OLEDs offer is an ability to produce a true blacks and lots of contrast without unduly increasing brightness.
Quantum dots: Also known as nanocrystals. When hit with any light of shorter frequency than that to be produced, these tiny semiconductors re-emit specific colors in strict relationship to their size. They are used in TVs to alter wide spectrum LED backlighting (that skews toward blue) into narrow-spectrum red, blue, and green light, producing warmer and more accurate colors.
Smart TV: A catch-all phrase to describe a TV that has computer-like abilities, including the ability to stream movies, browse the web, and play media across the network or from NAS boxes, or locally from USB hard drives or flash storage.
TN (twisted nematic): An older method of aligning the crystals in an LCD. In the off position, the crystals are in a twisted ladder parallel to the display surface, blocking the backlight. With power applied, the crystals are splayed perpendicular to the display surface, allowing light to emit forward, but still blocking much of its emission to the sides. Check for TN by viewing the display from a wide angle. If there’s any color shifting (purple-ness or washout), it’s a TN display (or an older IPS panel).
TFT (thin film transistor): Transistors, such as LCDs, or OLEDs, deposited in a thin coating on a sheet. Processes and materials vary, but peel open any flat-screen TV and you might be amazed that there are only what appear to be just a few sheets of plastic, some LEDs behind them, and a few small microchips. If you have a dead LED-backlit LCD TV, take a look inside before you recycle it. The technology is impressively simple.
Viewing angle (usable): The angle from which the picture on a display can be viewed without image or color distortion. When viewed from more than a slight angle, some cheaper TN or older IPS TVs will exhibit purple-ness, washout, or other color shifting artifacts. Screen coatings and glare affect viewing angles as well.
Don’t miss the other three installments in this series. In part one, we cover screen size, resolution, and speed; part three dispels the mysteries of color spaces and standards, and we wrap up the series with the lowdown on LCD backlighting tech.