TV tech terms demystified, part two: Display types and technologies
The first story in this series covers screen size, resolution, and speed. To read that story, which also discusses the mission behind this series, you can either click here or use the navigation tools at the top of this page.
The overall quality of TVs is astoundingly good these days, but there are still differences, mostly due to the type of technology used to build the TV. Here are the acronyms, buzzwords, and terminology you’ll want to understand.
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.
Active matrix/passive matrix: The pixels in all flat panel displays are addressed via a matrix of rows and columns. An active matrix refers consists of TFTs (Thin Film Transistors) that actively hold the state of the pixels using capacitors. An active matrix responds much quicker than a passive panel that uses 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 because it sounds cool.
CCFL (Cold Cathode Fluorescent lamp): The TV backlighting element from just a couple of years ago. CCFL made for thicker TVs, but it produced a flatter spectrum than the current blue-heavy LED backlighting.
Curved TV: A TV whose surface is slightly concave on the horizontal plane to create a sense of immersion, as well as reduce viewing angle artifacts. Some consider it more aesthetically appealing in terms of style—TVs are also furniture, after all—but this design sacrifices some of the space-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 shorter pulses to reduce motion blur. It's somewhat effective, but there's also a lot of marketing hype behind it.
Edge lighting: Placing a display’s backlight at the edge or edges of the screen, then channeling or distributing the light reflectively across the entire display. This is an older methodology that has been largely supplanted by rear backlighting.
Full Array: Simply an array of LED backlights spaced evenly behind the other flat-panel display components. We have no idea why "array" is preceded by "full;" we’ve never heard of a "partial" array backlighting system.
HDTV: The acronym stands for high-definition television, and it's applied to any TV with 720 or 1080 vertical resolution.
Halo: That little edge-lighting effect that you sometimes see when light-colored letters are superimposed on a very dark background. While this can be the sign of a cheaply made TV with light bleed, in truth it’s most often an effect created by the light passing through the fluid in your eyes. 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 from least- to most effective).
LCD (Liquid Crystal Diode): A low-power, miniature electronic shutter consisting of crystals suspended in liquid. When powered, 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 which produce their own colored light, LCDs are transparent and pass through only the red, green, and blue light created by filters placed behind them.
LCD TV: A TV that uses LCD technology. Generally, it will consist of a backlight, a light-tunnel or similar diffusion layer to even distribute the backlight; a filter layer to change the broad spectrum LED light into red, green, and blue; and the LCDs that 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 larger size and power draw, LEDs are employed as backlights in TVs rather than as primary display elements.
LED zone: The area 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: These days, this generally refers to an LCD TV with LED backlighting. 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 does produce a bright picture, and with quantum dots involved, as rich a color palette as an OLED.
Local dimming: Turning off or dimming the LED backlight/backlights 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 produce banding and other artifacts. Dimming requires multiple LED backlights and isn’t applicable to OLED TVs, which don’t need backlighting.
Motion Blur: While no longer common, 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. These are used in TVs, computer, and mobile device displays.
OLED TV: A TV that uses OLEDs to provide both light and color. At the time of this writing, OLED is most expensive type of flat-panel TV 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 black. Since there is no backlight, no light is produced when an OLED pixel is turned off. This also helps increase contrast when other colors are displayed next to black.
Quantum dots: Also known and advertised as nanocrystals. When hit with a broad spectrum light (actually 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, blue-heavy LED backlighting into narrow-spectrum red, blue, and green light to produce 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 locally or network-attached mass storage such as hard drives or flash drives.
TN (Twisted Nematic): An older method of aligning the crystals in a 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 at a wide angle. If there’s any color shifting (purple-ness or washout), it’s TN or older IPS.
Though TN has improved, you want IPS, and while it may or may not be mentioned in the advertising or specs, you can easily tell if it’s present by viewing the display from a very wide angle. If there’s purple-ness (color shift) or washout, it’s not IPS or it’s a very old version.
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 to find only what appears to be just a few sheets of plastic, some LEDs behind them, and a few small microchips. It's kind of like magic.
Viewing angle: 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.