Steve Kindig has been an electronics enthusiast for over 30 years. He has written extensively about home and car A/V gear for Crutchfield since 1985. Steve is also a volunteer DJ at community radio station WTJU, where he is a regular host of the American folk show "Atlantic Weekly," as well as the world music program "Radio Tropicale."
More from Steve Kindig
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10-bit display panel
See color resolution.
1080p is a high-definition video format with resolution of 1920 x 1080 pixels. The "p" stands for progressive scan, which means that each video frame is transmitted as a whole in a single sweep. The main advantage of 1080p TVs is that they can display all high-definition video formats without downconverting, which sacrifices some picture detail.
1080p TVs display video at 60 frames per second, so this format is often referred to as 1080p60. The video on most Blu-ray discs is encoded at film's native rate of 24 frames per second, or 1080p24. For compatibility with most current 1080p TVs, high-definition players internally convert the 1080p24 video to 1080p60. By late 2007, many HDTVs included the ability to accept a 1080p24 signal directly. These TVs don't actually display video at 24 frames per second because that would cause visible flicker and motion stutter. The TV converts the video to 60 frames per second or whatever its native display rate is. The ideal situation would be to display 1080p24 at a multiple of 24 frames per second, like 72, 96, or 120 frames per second, to avoid the motion judder caused by 3-2 pulldown, which is required when converting 24-frames-per-second material to 60 frames per second.
120Hz refresh rate
Some LCDand LED HDTVs have 120Hz refresh rates; these TVs employ sophisticated video processing to double the standard rate to 120 frames per second by inserting either additional video frames or black frames. Because each video frame appears for only half the normal amount of time, on-screen motion looks smoother and more fluid, with less smearing. It's especially noticeable viewing fast-action sports and video games. This feature is available on an increasing number of flat-panel LCD TVs.
Watch our video about LCD refresh rates for more info.
240Hz refresh rate
240Hz refresh rate reduces LCD motion blur on LCD TVs even more than 120Hz refresh rate. 240Hz processing creates and inserts three new video frames for every original frame. Most "240Hz" TVs operate this way, but some models use "pseudo-240Hz" technology which combines 120Hz refresh rate with high-speed backlight scanning. An example of the pseudo-240Hz approach, which can also be very effective, is Toshiba's ClearScan 240™ technology.
Watch our video about LCD refresh rates for more info.
|Want to watch 3D at home? You'll need a 3D TV, a pair of 3D glasses for each viewer, and a 3D video source.|
By adding a sense of picture depth and dimensionality, 3D TVs create a more engaging viewing experience that's similar to watching a 3D movie in a theater. Like 3D movies, 3D TV requires that each viewer wear special glasses to see the 3D effects. Most 3D TVs require the use of battery-powered "active shutter" glasses, though some TVs work with lightweight passive glasses that are virtually identical to the glasses handed out in movie theaters.
Whether a 3D TV uses LCD or plasma screen technology, the basic idea at work in all 3D TVs is creating "left" and "right" versions of the image on screen. The tricky part is getting the correct version of the image to the correct eye. That's the job of 3D glasses. Whether your TV uses active shutter glasses or polarizing passive glasses, your brain combines the images it receives from your right and left eyes into a seamless whole, just like it does when you look at the world around you.
3-2 pulldown processing
Sophisticated video processing common in HDTVs and progressive-scan DVD players. It corrects for artifacts and distortion that occur when film-based material (at 24 frames per second) is converted to video (30 frames per second), then de-interlaced to create a progressive-scan signal. For a more in-depth explanation, see our DVD Player Glossary.
See aspect ratio.
4:4:4 (4:2:2, 4:2:0)
See chroma subsampling.
Refers to high-resolution digital displays and video formats with horizontal resolution of around 4000 pixels. 4K projectors have been used in movie theaters for many years. At the end of 2012, the first flat-panel HDTVs with 4K screen resolution appeared. The pixel count for these TVs is 3840 x 2160, which is twice the horizontal and vertical resolution of 1080p (1920 x 1080 pixels). 4K has four times the total pixels of 1080p and is capable of creating a much more detailed picture. As of this writing (12/12) there is no true 4K content available, although 4K TVs include video processing that upconverts lower-resolution sources to 4K.
4K is also known as Ultra High Definition TV.
600Hz sub field drive
Plasma TVs that are labeled "600Hz" employ technology which plasma TV makers generally refer to as 600Hz sub field drive. Although it does help plasmas produce smooth video motion, this technology works differently than the 120Hz and 240Hz refresh rates used by LCD TVs.
A plasma panel has extremely fast pixel response time — just a fraction of a millisecond. That's much faster than is needed to display the incoming video signal, which is generally 60 frames per second. So, to display a single video frame for 1/60 of a second, a plasma panel fires the pixels in pulses in order to keep all the pixels "hot" so they can continuously display the video image. A plasma with 600Hz sub field drive produces 10 pulses per frame, so the picture is being refreshed at 60 frames per second times 10 pulses per frame, which equals 600Hz. Earlier plasmas fired their pixels at 8 pulses per frame for a refresh rate of 480Hz. This super-fast sub field refresh rate allows plasma TVs to make virtually instantaneous transitions from frame to frame, which minimizes motion blur. See our FAQ on 600Hz plasmas for more info.
|Active 3D TVs required battery-powered active glasses to create the 3D effect.|
Active shutter glasses
To see three-dimensional effects on most 3D TVs, each viewer must wear a special type of 3D glasses called "shutter" glasses. Also called "active" glasses, these battery-powered liquid-crystal glasses are able to lighten or darken hundreds of times per second to alternately block out the left or right lens in coordination with the video frames flashing on screen. The lenses aren't displaying images, just switching between dark and clear. To anyone not wearing shutter glasses, a 3D TV picture will look blurry. Active glasses are far more technologically advanced than the disposable 3D glasses handed out in movie theaters. A few 3D TVs do use passive 3D glasses though.
After image (image retention)
Nearly any TV these days — LCD, plasma, or LED-LCD — has the ability to briefly retain an image. For example, if you were watching something in a squarish 4:3 aspect ratio, you might notice the faint outline of the black bars on the sides when you change to a 16:9 image. Unless you leave the exact same image up for a very, very long time (think days if not weeks), these "after images" are temporary. So if you do notice this kind of mild image retention in your TV, don't worry — in most cases, they'll disappear within minutes. Also see "burn-in."
Refers to widescreen video images that have been "squeezed" to fit a narrower video frame when stored on DVD. These images must be expanded (un-squeezed) by the display device. Most of today's TVs employ a screen with 16:9 aspect ratio, so that anamorphic and other widescreen material can be viewed in its proper proportions. When anamorphic video is displayed on an old-fashioned TV with a 4:3 screen, images appear unnaturally tall and narrow.
A technology that reduces image "smearing" or "motion blur" that can sometimes occur with LCD or LED TVs. LCD televisions with anti-blur technology can deliver smoother, cleaner images than those without, particularly during fast-paced scenes. This anti-blur video processing is usually described as 120Hz refresh rate or 240Hz refresh rate. The highest actual refresh rate available on current TVs (as of 12/12) is 240Hz. Sometimes a high refresh rate is combined with high-speed backlight scanning, and manufacturers may refer to this as "480," "720," or higher motion processing. TV makers have their own proprietary names for anti-blur technology; examples include Sony's Motionflow™ and Samsung's Auto Motion Plus.
Watch our video about LCD refresh rates for more info.
Unwanted visible effects in the picture created by disturbances in the video transmission or processing. Examples include "dot crawl" or "hanging dots" in analog pictures, or "pixelation" in digital pictures.
The ratio of width to height for an image or screen. The North American NTSC television standard uses the squarish 4:3 (1.33:1) ratio. HDTVs use the wider 16:9 ratio (1.78:1) to better display widescreen material like high-definition broadcasts and DVDs. See our article about aspect ratio to better understand it and get pointers on troubleshooting some common aspect ratio problems.
ATSC (Advanced Television Standards Committee)
Formed to establish technical standards for the U.S. digital television system. A TV tuner that can receive local over-the-air digital broadcasts is often called an ATSC tuner.
Audio Return Channel
This feature is found on most 2010-and-newer TVs and audio/video components with HDMI 1.4 connections. A TV with Audio Return Channel allows a single HDMI cable to carry the audio from the TV's built-in tuner "upstream" to a compatible A/V receiver, eliminating the need for a separate optical or coaxial digital audio cable.
Using a TV's direct audio/video inputs to connect a DVD player, VCR, camcorder or other video component provides improved picture and sound quality compared to using the everything-on-one-wire RF antenna-style input. If your TV is old enough that it only has RF-type inputs, that's reason enough to consider replacing it, since many newer video components don't include an RF output.
For more info, read our article about connecting your HDTV.
An anti-blur technology used in many LCD TVs. When a TV's backlight — either LED or fluorescent — shines continuously, it can contribute to motion blur. LCD models with backlight scanning use a backlight that pulses at very high speed, which has the effect of reducing motion blur. Some recent TVs use backlight scanning along with fast refresh rates for even greater blur reduction.
The maximum amount of information that can be transferred in a given amount of time. More detailed video requires more bandwidth. For example, high-def 3D video signals require much more bandwidth than standard-definition DVD video signals. This is why you need to have certain kinds of cables to pass high-quality video — not all cables are capable of carrying those higher bandwidths.
Measured as "bits per second," and used to express the rate at which data is transmitted or processed. The higher the bitrate, the more data is processed and, typically, the higher the picture resolution. Digital video formats typically have bitrates measured in megabits-per-second (Mbps). (One megabit equals one million bits.) The maximum bitrate for standard DVDs is 11Mbps; for over-the-air HDTV broadcasts, it's 19.4Mbps. Blu-ray discs have an even higher maximum bitrate of 54Mbps.
Describes the appearance of darker portions of a video image. Black is the absence of light, so to create the black portions of an image, a display must be able to shut off as much light as possible. Displays with good black level capability not only produce deeper blacks, but also reveal more details and shading in dark or shadowy scenes. Plasmas are generally known for having excellent black levels, since they can shut off pixels entirely. LED TVs with local dimming can also have very good black levels, since they can individually dim portions of the LED backlight behind the screen.
Screen burn-in was an issue for early plasma TVs. It could occur when a static image — like a non-widescreen 4:3 image with vertical black bars on the sides, or a scrolling stock or news ticker — remains on-screen for an extended period. These images could become etched into the screen's phosphor coating, leaving faint impressions.
In recent years, TV makers have significantly reduced plasma power consumption and refined the panel technology to dramatically reduce the chances of burn-in occurring, while also including the ability to erase burn-in effects. New plasma TVs are virtually immune to screen burn-in. (In fact, many avid gamers at Crutchfield use plasmas for video games — notoriously burn-in-prone material — and haven't had any problems.) Of course, to prevent any possibility of burn-in, plasma owners should follow the manufacturer's guidelines for adjusting the TV's brightness and contrast settings when the TV is new. For tips on TV settings, see our article about optimizing your TV's picture.
Images are made up of pixels, and each pixel contains two types of information: luminance or luma, which is brightness, and chrominance or chroma, which is color. Because our eyes are less sensitive to color detail than to brightness detail, chroma subsampling is used to reduce the amount of data in a video signal while having little or no visible impact on image quality.
Video created with chroma subsampling still includes brightness information for every single pixel, but not color information. Color information is shared among adjacent pixels. The number of pixels that share the same color information is determined by the type of chroma subsampling. To describe the extent of subsampling, video professionals use a numerical shorthand that references a block of 8 pixels, 4 across and 2 high.
This shorthand has three numbers separated by colons. The first number indicates the number of pixels wide the sample is (usually 4). The second number tells you how many of the pixels in the top row will have color information, that is, chroma samples. And the third number tells you how many pixels in the bottom row will have chroma samples. Here are some common examples:
- 4:4:4 - in this case, every pixel gets a chroma sample so there is no subsampling happening. This is uncompressed color.
- 4:2:2 - here, every two pixels in the top row have to share a chroma sample, and every two pixels in the bottom row have to share a chroma sample, which means that 50% of the color information is being thrown out.
- 4:2:0 - this is more aggressive subsampling where again every two pixels in the top row share a chroma sample, but in this case, the bottom row has no color information of its own, and has to share the chroma samples of the top row. 75% of the color information is discarded.
Of course, the easy assumption is that more is better, but 4:4:4 color is considered overkill for consumer video — it's considered high end even for professional video. 4:2:2 color is also more commonly used by pros. Despite its significant color compression, 4:2:0 can still produce great image quality. It's the format used by Blu-ray. Consumers who connect a PC to their TVs for gaming will be more interested in chroma subsampling since many high-performance video cards support 4:4:4.
The color component of a video signal that includes information about hue (shade) and saturation (intensity).
Color resolution (color bit depth)
The color resolution of TVs and other video gear is typically described as a color bit depth such as "8-bit" or "10-bit." Color resolution indicates how fine the gradations can be between different shades of the same color — it's a measure of color accuracy. Nearly all consumer video equipment is 8-bit, and 8-bit resolution allows 256 possible shades. That's 256 each for the red, green, and blue primary colors. To calculate the total number of possible colors an 8-bit TV can reproduce, you multiply 256 x 256 x 256, which equals 16.7 million. Some TVs use 10-bit panels and video processing. That may not sound like much more, but 10-bit resolution means 1024 possible shades and over one billion total colors.
A "color space" is a defined range of colors, and is usually associated with an industry standard. Examples of color spaces that relate to television and video equipment include NTSC for analog video, and ATSC and x.v.Color for high-definition video. A wider color space offers the potential for deeper hues. If you see a TV's color range expressed as a percentage of a color space, it's almost always NTSC.
|Component video cables are the only analog video cables capable of carrying a high-def signal. They're a great alternative if HDMI isn't available.|
The three-jack component video connection splits the video signal into three parts (one brightness and two color signals). Compared to other analog video connections, component video has increased bandwidth for color information, resulting in a more accurate picture with clearer color reproduction and less bleeding. Component video is the only type of analog video connection that can pass high-definition signals, and provides better picture quality than S-video or composite video connections. Also see our connections glossary.
For more info, read our article about connecting your TV.
Composite video won't give you a very sharp picture, so you shouldn't use it unless higher-quality connections like HDMI and component video aren't available.
A single video signal that combines brightness and color information. A composite signal is better than an RF signal, but not as good as S-video. A composite video jack is usually a single RCA-type. Also see our connections glossary.
For more info, read our article about connecting your TV.
Measures the difference between the brightest whites and the darkest blacks that a TV can display. The higher the contrast ratio, the better a TV will be at showing subtle color details, and the better it will look in rooms with more ambient room light. Picture contrast is one of the most important contributors to a TV's picture quality, but the contrast ratio specs supplied by TV makers should be taken with a large grain of salt.
There are actually two different ways of measuring a TV's contrast ratio. Static contrast ratio measures the difference between the brightest and darkest images a TV can produce simultaneously (sometimes called on-screen or native contrast ratio). The ratio of the brightest and darkest images a TV can produce over time is called dynamic contrast ratio. Dynamic contrast ratio can be many times higher than static.
There are no universally accepted methods of measuring contrast ratio, and TV makers use different approaches when measuring their products. For that reason, contrast ratio isn't very useful when you're shopping for a TV. It's really only meaningful when you're comparing TVs from the same manufacturer.
For more info, see our video about TV contrast ratio.
CRT (Cathode-Ray Tube)
A CRT ("picture tube") is a specialized vacuum tube in which images are created when an electron beam scans back and forth across the back side of a phosphor-coated screen. Each time the beam makes a pass across the screen, it lights up a horizontal line of phosphor dots on the inside of the glass tube. This beam rapidly draws hundreds of these lines from the top to the bottom of the screen, creating the image.
The old-fashioned "direct-view" TVs most people grew up watching have a single large picture tube, while CRT-based rear-projection and front-projection TVs use three CRTs: one each for the red, green, and blue primary colors.
A color resolution standard associated with high-definition TVs and video gear that include HDMI 1.3 connections. Deep Color supports 10-bit, 12-bit and 16-bit color bit depths, up from 8-bit, which is the current standard for consumer video. All earlier versions of HDMI supported 8-bit color. (Because video is based on three primary colors, you'll sometimes see Deep Color described as 30-bit, 36-bit and 48-bit.) A higher color bit depth enables finer gradations between different shades of the same color, for smoother gradients and reduced color banding.
Deep Color gives TVs the potential to display billions rather than millions of colors, but in order to see that improvement, the entire video production chain has to use it (camera, editing, format, player, display). Right now, there isn't any Deep Color video content available. So if you want to watch Deep Color video, your only option is to shoot your own with a Deep Color-capable camcorder, then connect it to a Deep Color-capable TV. Also see color resolution.
The process of converting an interlaced-scan video signal (where each frame is split into two sequential fields) to a progressive-scan signal (where each frame remains whole). De-interlacers are found in TVs, DVD players, and Blu-ray players. More advanced de-interlacers include a feature called 3-2 pulldown processing.
A lot of TVs let you send surround sound from HDTV broadcasts back to your receiver via an optical digital audio cable.
Digital audio output
A connection found on HDTVs for sending the Dolby Digital soundtrack of HD broadcasts to an A/V receiver with Dolby Digital decoding. These days, many TVs feature an optical digital audio output for this purpose. Some newer TVs also have a feature called "Audio Return Channel" that lets you send audio back to your receiver via HDMI.
DLNA, short for Digital Living Network Alliance, is a collaboration among more than 200 companies, including Sony, Panasonic, Samsung, Microsoft, Cisco, Denon and Yamaha. Their goal is to create products that connect to each other across your home network, regardless of manufacturer, so you can easily enjoy your digital and online content in any room.
While all DLNA-compliant devices are essentially guaranteed to work together, they may not be able to share all types of media. For example, a DLNA-certified TV may be able to display digital photos from a DLNA-certified media server, but not videos. See our article on streaming music, photos and videos from your computer to your TV for more info.
DLP™ (Digital Light Processing)
A projection TV technology developed by Texas Instruments, based on their Digital Micromirror Device (DMD) microchip. Each DMD chip has an array of tiny swiveling mirrors which create the image. Depending on the TV's resolution, the number of mirrors can range from several hundred thousand to over two million. DLP technology is used in both front- and rear-projection displays.
There are two basic types of DLP projector. "Single-chip" models use a single DMD chip, with color provided by a spinning color wheel or colored LEDs. "3-chip" projectors dedicate a chip to each primary color: red, green, and blue. While 3-chip models are considerably more expensive, they completely eliminate the rainbow effect, which is an issue for a small minority of viewers.
A discrete multichannel digital audio format that is the official audio standard for HDTV (and DVD). Dolby Digital is normally associated with 5.1-channel surround sound. Though this channel configuration is the most common, it is only one of several possible variations — a Dolby Digital soundtrack can mean anything from 1 to 5.1 channels. To learn about the various surround sound options available, see our article about surround sound formats.
All digital TV display technologies have screens with a fixed number of pixels for displaying images. If a video source has a higher resolution than the screen's resolution, the TV will automatically downconvert the video signal to fit the screen. Downconversion reduces image detail, but downconverted pictures can still look very sharp. A good example is a 1080i TV broadcast displayed on a 720p TV.
DTV (Digital Television)
A general term for the ATSC digital broadcast TV standard, which replaced the NTSC analog broadcast system. DTV comes in two basic flavors: widescreen, high-quality HDTV (High-Definition Television) with Dolby Digital audio, and medium-quality SDTV (Standard-Definition TV).
|HDMI-to-DVI adapters are essential if you want to connect a DVI-equipped component (like a computer or older DVD player) to a newer TV.|
DVI (Digital Visual Interface)
A multi-pin, computer-style connection intended to carry high-resolution video signals from video source components (such as older HD-capable satellite and cable boxes, and upconverting DVD players) to HD-capable TVs with a compatible connector. Most (but not all) DVI connections use HDCP (High-bandwidth Digital Content Protection) encryption to prevent piracy. In consumer electronics products, DVI connectors have been almost completely replaced by HDMI connectors, which carry both video and audio. You can use an adapter to connect a DVI-equipped component to an HDMI-equipped TV, or vice versa, but a DVI connection can never carry audio. That means that if you use an HDMI-to-DVI adapter to connect a new Blu-ray player to an older HDTV, you'll still need to make an separate audio connection, because the DVI adapter can't pass on the audio signal from the HDMI cable. See our connections glossary for more info.
Found on many LCD TVs, this feature dynamically adjusts the brightness of the backlight in response to the picture content of whatever you're watching, to improve picture contrast and reduce power consumption. It helps the TV display both bright outdoor scenes and dark indoor scenes with greater accuracy. Use of dynamic backlighting contributes to the very high "dynamic contrast ratio" specs provided by TV makers.
EDTV (Enhanced-Definition Television)
A virtually obsolete class of televisions, generally flat-panel LCD or plasma, that displays signals in 480-line progressive-scan (480p) mode. 480p screen resolution is superior to standard analog TV (480i), but not as sharp as true HDTVs (720p or 1080p).
Electronic program guide (EPG)
Provides an on-screen listing of available channels and program data for an extended time period (typically 36 hours or more). Examples of program guides include subscription services like TiVo® and free guides like TV Guide® On Screen.
Emitter (for 3D TV)
An important part of every active 3D TV is the built-in "emitter" that precisely controls the timing of the active shutter glasses. The emitter communicates with the glasses wirelessly via either infrared beams, RF, or Bluetooth®.
ENERGY STAR® compliant
A certification for consumer electronics products indicating energy efficiency. The Energy Star program was introduced by the EPA (Environmental Protection Agency) in 1992, and set standards for product power consumption in "standby" mode. (When a component is switched off but still plugged into an AC power source, it continues to draw a small amount of power in standby mode to keep circuits active and ready for quick turn-on.) Over the years the EPA has created ever more stringent ENERGY STAR specifications. For 2012, ENERGY STAR certified TVs are, on average, more than 20 percent more energy efficient than conventional models. The requirements for larger-screen TVs are even more stringent. For example, an ENERGY STAR certified 60" TV will be, on average, nearly 40 percent more efficient than a non-certified model.
An Ethernet port on a TV enables a connection to a home network and/or the Internet. What you can do once you're on the network varies by model. Some TVs will let you play music or videos from your computer, or stream music or movies from services like Pandora® or Netflix®. See Internet-ready TVs for more info.
In interlaced-scan video, each complete frame is split into 2 sequential fields, each of which contains half the picture information. One field contains the odd scanning lines, and the other field the even lines.
In moving picture media, whether film or video, a frame is a complete, individual picture.
The rate at which frames are displayed. The frame rate for movies on film is 24 frames per second (24 fps). Standard NTSC video has a frame rate of 30 fps (actually 60 fields per second). The frame rate of a progressive-scan video format is twice that of an interlaced-scan format. For example, interlaced formats like 480i and 1080i deliver 30 complete frames per second; progressive formats like 480p, 720p and 1080p provide 60.
Measures the light-reflecting ability of a projection screen. The higher the number, the greater the amount of light reflected back to the viewer(s).
HDCP (High-Bandwidth Digital Content Protection)
HDCP encryption is used with high-resolution signals over DVI and HDMI connections and on D-Theater D-VHS recordings to prevent unauthorized duplication of copyrighted material.
A high-quality HDMI cable will let you enjoy high-resolution audio from your Blu-ray discs.
HDMI™ (High-Definition Multimedia Interface)
HDMI has become the high-def connection of choice. It can carry full 1080p video and multichannel surround sound, and is your only connection option for 3D video. For more info, read our article about connecting your TV, or get an in-depth look at HDMI in our article covering all the details about HDMI.
A remote control protocol that is an optional part of the HDMI spec — CEC stands for "Consumer Electronics Control." Available from HDMI version 1.2a on, HDMI-CEC allows multiple HDMI-connected components to be operated from a single remote control without any special setup or programming. HDMI-CEC is a 2-way communications system, and up to 10 devices can be controlled in a system. Each electronics manufacturer calls this feature something different: Panasonic uses EZ-Sync, Samsung Anynet+, Sony BRAVIA Theatre Sync, Toshiba CE-LINK, LG SimpLink, etc.
HDTV (High-Definition Television)
Often mistakenly used as a generic description of all digital television, HDTV specifically refers to the highest-resolution formats of the 18 original DTV formats. Although there still isn't 100% agreement among manufacturers, retailers, journalists, etc., only 1,080-line interlaced (1080i) or 720-line progressive (720p) broadcasts are generally considered to be true HDTV. 1,080-line progressive (1080p) is not an official HD broadcast format, but it is found on high-definition Blu-ray discs and some satellite TV movie broadcasts. And 1080p is now an established standard for HDTV screens.
A measure of frequency. One Hertz equals one cycle per second. In video, Hertz is used to describe a frame rate in frames per second. For example, you'll often see 24-frames-per-second video at listed as "24Hz."
Interlaced scan is a way to describe how some video signals and displays form an image. America's NTSC analog television system uses 525 scanning lines to create each complete picture (frame). The frame/picture is made up of two fields: The first field has 262.5 odd lines (1,3,5...) and the second field has 262.5 even lines (2,4,6...). The odd lines are scanned (drawn on the screen) in 1/60th of a second, and the even lines follow in the next 1/60th of a second. This presents a complete frame/picture of 525 lines in 1/30th of a second.
Analog NTSC video uses interlaced scanning, as do some digital television (ATSC) formats. Formats that include an "i" (1080i, 480i) use interlaced scanning. In fact, these days interlaced scanning is mostly mentioned when describing video broadcasts because virtually all non-tube TV types are progressive scan by nature. For a more complete discussion of interlaced vs. progressive scan, see our article or video about HDTV resolution.
|Internet-ready TVs can connect to your home network. Different TV makers provide access to different Internet sites and services, but many of today's sets give you access to things like Netflix® and YouTube™.|
TVs labeled "Internet-ready" can connect to your home network to access online content. For example, a growing number of Internet-ready TVs let you play movies from services like Netflix®, BlockBuster™, or Amazon Video On Demand™. Basic Internet-ready models may limit your access to web sites and services to those that the TV manufacturer has partnered with.
If you do want full Internet access from your TV, look for "smart" models. These sets have a complete Internet browser, so you can surf the web much as you would on your laptop.
Most current Internet-ready TVs include Wi-Fi® connectivity for no-hassle hookup.
"Keystoning" is a form of video image distortion that occurs with front projectors if the centerline of the projector's lens is not perpendicular to the screen. Keystoning results in an image which is shaped like a trapezoid rather than a rectangle — the top of the picture is wider than the bottom, or the left side is taller than the right, for example. Most front projectors include "keystone correction" to correct this distortion. Some models have vertical keystone correction, while others include both vertical and horizontal correction. Although keystone correction allows greater mounting flexibility, it is a form of processing which usually has a slight softening and dimming effect on the picture.
See our article on projectors for more info.
LCD (Liquid Crystal Display)
Most of today's flat-panel TVs use Liquid Crystal Display technology, and it's also found in some projectors. Light isn't created by the liquid crystals; a "backlight" shines light through the display. The display consists of two polarizing transparent panels and a liquid crystal solution sandwiched in between. An electric current passed through the liquid causes the crystals to align so that light cannot pass through them. Each crystal acts like a shutter, either allowing light to pass through or blocking the light. The pattern of transparent and dark crystals forms the image.
LCoS (Liquid Crystal on Silicon)
A digital projection TV technology based on LCD. With LCoS, light is reflected from a mirror behind the LCD panel rather than passing through the panel. The control circuitry that switches the pixels on and off is embedded further down in the chip so it doesn't block the light, which improves brightness and contrast. This multilayered microdisplay design was used in rear-projection TVs, and continues to be used in high-performance home theater projectors by Sony and JVC.
LED (Light Emitting Diode)
An LED is a semiconductor diode that typically emits a single wavelength of light when an electric current passes through it. Different colors can be generated based on the material used; common colors include red, green, blue, and white. Most current LCD TVs use white LEDs for backlighting.
|LED TVs use the same liquid crystal technology as regular LCDs, but with an LED backlight. These TVs are often more energy efficient and provide better color accuracy than fluorescent-backlit LCD TVs.|
A term sometimes used for LCD TVs that use an LED backlight instead of a conventional fluorescent one. An LED backlight improves contrast and delivers a wider range of colors, for a more lifelike picture. TVs with LED backlights also generally consume less power than those that use fluorescent backlights.
Some of these TVs use a series of LEDs arranged in a grid behind the LCD panel. And some TVs with these LED grids feature "local dimming", which allows the TV to display light and dark portions of the same image more accurately. Other sets are "edge-lit," meaning that the LEDs are located around the sides of the panel instead of in a grid behind it. While edge-lit LED TVs may offer a more limited form of dimming, they generally have thinner cabinets — sometimes barely more than an inch deep. For more information, see our video on LCD backlighting.
A method for displaying the entire picture as seen in a movie theater on a TV screen. The resulting image width is much greater than its height. On an old-fashioned TV screen with 4:3 aspect ratio, letterboxed videos appear with horizontal black bars above and below the image. You will often see these black bars when watching movies on a widescreen TV, too. To learn more about aspect ratios and ways to deal with those black bars, see our aspect ratio article.
Measures the amount of light produced by a video display, and is an especially important spec for projectors. Expressed in "lumens" or "ANSI lumens," with a higher number indicating greater light output, which results in a brighter picture.
A feature found on some LED-backlit TVs that allows them to dim or even completely shut off different sections of the LED backlight. These TVs can accurately display both light and dark portions of an image at the same time, for greater contrast and a more lifelike picture. See our video on LCD backlighting for more info.
The unit of measure for light output of a projector. Different manufacturers may rate their projectors' light output differently. "Peak lumens" is measured by illuminating an area of about 10% of the screen size in the center of the display. This measurement ignores the reduction in brightness at the sides and corners of the screen.
The more conservative "ANSI lumens" (American National Standards Institute) specification is made by dividing the screen into 9 blocks, taking a reading in the center of each, and averaging the readings. This number is usually 20-25% lower than the peak lumen measurement.
The brightness or black-and-white component of a color video signal. Determines the level of picture detail.
Equal to one million Hertz. Video signal bandwidth is typically expressed in megahertz.
A general term covering several different technologies used in digital rear-projection TVs and projectors. These displays produce large images; the "micro" refers to the postage stamp-sized image chips that create the images. Microdisplay types include DLP, LCD, and LCoS. As of this writing (12/12), the last remaining manufacturer of rear-projection TVs — Mitsubishi — has announced that they will stop building rear-projection models.
MPEG (Moving Picture Experts Group)
The organization charged with developing video and audio encoding standards. On the video front, consumers are most likely to encounter the MPEG-2 and MPEG-4 compression formats, or "codecs." These formats are capable of producing very high quality video by employing an adaptive, variable bitrate process that can allocate more bits for complex scenes involving a lot of motion, while reducing the bits in static scenes.
- MPEG-2: Used for over-the-air digital television broadcasts, standard DVDs, some Blu-ray Disc discs and small-dish satellite TV (DIRECTV and DISH).
- MPEG-4: This newer format is more efficient than MPEG-2, meaning it can deliver the same picture quality as MPEG-2 using a lower bitrate. Some Blu-ray Discs and newer DIRECTV and DISH satellite gear use MPEG-4.
NTSC (National Television System Committee)
The North American 525-line analog broadcast TV standard, which was established over 50 years ago. Although it is referred to as a "525-line" standard, we're only able to see 480 lines on a TV display. The ATSC digital broadcast standard replaced NTSC on June 12, 2009.
OLED (Organic Light Emitting Diode)
OLED is a display technology that has been used for high-end smartphone screens for a few years, and is now becoming available on large-screen TVs. An OLED panel employs a series of organic thin films placed between two transparent electrodes. An electric current causes these films to produce a bright light. A thin-film transistor layer contains the circuitry to turn each individual pixel on and off to form an image. The organic process is called electroluminescence, which means the display is self-illuminating, requiring no backlight. OLED panels are thinner and lighter than current plasma or LCD HDTVs, and consume less power.
The portion of a video image that lies outside a TV's visible screen area. The amount of overscan varies from model to model, but typically ranges between 5% and 10% or the total image. Some recent TVs with "pixel-by-pixel" or "dot-by-dot" display modes are capable of showing the full image, with no overscan. This is especially advantageous when viewing 1080i or 1080p content on a 1080p TV.
The process of transferring a widescreen movie or other source material to videocassette, DVD, or broadcast so that it fits the squarish 4:3 aspect ratio of most old-fashioned TVs. This results in a significant amount of lost picture information, particularly in the width of the image. Most new HDTVs use the wider 16:9 aspect ratio, which can display all or most of the original picture of widescreen material.
At the beginning of some older DVD movies, you'll usually see a disclaimer about the movie having been "...formatted to fit your TV." That means it's been converted to pan-and-scan.
Passive 3D glasses
Although most 3D TVs require active shutter glasses, a few work with passive 3D glasses. Unlike active glasses, passive glasses don't require a battery. Also, passive glasses don't flicker — an issue that distracts some viewers with active glasses.
There are two flavors of picture-in-picture: 1-tuner PIP models require that you connect a VCR or other video component to provide the source for your second picture. 2-tuner PIP models have two built-in TV tuners, so you can watch two channels at once using only the TV.
Originally, PIP allowed viewing of multiple channels or sources by creating a small inset image overlaid on the main image. With the shift to widescreen displays, the inset type of PIP is gradually being replaced by "split screen" designs that are sometimes referred to as POP (picture-outside-picture) or PAP (picture-and-picture).
The pillar-box effect occurs in widescreen 16:9 video displays when vertical black bars are placed at the sides of a non-widescreen 4:3 image. The smaller the size of the pixels in an image, the greater the resolution. To learn more about aspect ratios and ways to deal with black bars, see our aspect ratio article.
|When 4:3 programs are displayed on a 16:9 screen, black or gray bars appear on the sides of the screen — the image is "pillar-boxed."|
Short for "picture element." The smallest bit of data in a video image. As pixel size gets smaller, more pixels can fit in the same screen area, increasing picture resolution.
Pixel response time
The amount of time it takes for a single pixel in a video display to switch from active to non-active; it is measured in milliseconds (ms). If a display's response time is too slow, faint motion trails may be visible following fast-moving on-screen objects. Fast pixel response is important for all types of flat-panel TVs. It's not mentioned as much anymore for LCD TVs because most models use fast screen refresh rates (120Hz, 240Hz) or backlight scanning to reduce motion blur.
|Plasma TVs don't sell as well as LCDs despite generally offering better black levels, wider viewing angles, and more natural-looking on-screen motion. And plasmas usually cost less than an LCD of similar size and features.|
Plasma technology is one of the methods used to create flat-panel TVs. The display consists of two transparent glass panels with a thin layer of pixels sandwiched in between (just over two million pixels for a 1080p screen). Each pixel is composed of three gas-filled cells or sub-pixels (one each for the red, green and blue primary colors). A grid of tiny electrodes applies an electric current to the individual cells, causing the gas to ionize. This ionized gas (plasma) emits high-frequency UV rays which stimulate the cells' phosphors, causing them to glow, which creates the TV image. For more info on how plasma technology works, see our LCD vs. Plasma article. You can also check out our video comparing LCD and plasma TVs.
Some digital television broadcast formats (720p, 480p), and virtually all current Blu-ray players, use a type of video signal known as progressive scan. Instead of splitting each video frame into two sequential fields like analog interlaced NTSC video, progressive-scan video displays the entire frame in a single sweep. For example, where standard NTSC video displays 30 frames (60 fields) per second, progressive scan displays 60 complete frames per second.
Another way to look at it is that progressive-scan video has twice as much picture information as the equivalent interlaced video format. Progressive-scan picture quality is more filmlike, with more fine detail and less flicker. Virtually all of today's digital TVs are progressive-scan displays, with screen resolutions of 720p, 768p or 1080p. For a more in-depth discussion of progressive vs. interlaced scan, see our article about video resolution.
|Front projectors are great if you want a true theater experience — a screen 10 feet across, or more.|
A video display device that projects a large image onto a physically separate screen. The projector is typically placed on a table, or ceiling-mounted. Projectors, sometimes referred to as front-projection systems, can display images up to 10 feet across, or larger. Old-fashioned large, expensive CRT-based projectors have been replaced by compact, lightweight, lower-cost digital projectors using LCD technology.
QAM (Quadrature Amplitude Modulation)
A digital modulation format used for downstream transmission in cable TV systems — commonly used for cable HDTV.
A QAM tuner allows cable subscribers to tune in unscrambled cable channels without a separate set-top box, including high-definition channels, if the cable service provider offers them.
A visual artifact associated with single-chip DLP-based rear- and front-projection displays. Fortunately, only a few people see these momentary flashes of color, and fewer still find these "rainbows" to be distracting. For those unlucky few, rainbows typically occur when the viewer's eyes dart away from the screen. Rainbows result from DLP's use of a color wheel, which causes the three primary colors — red, green, and blue — to be projected sequentially, rather than continuously. Rainbows aren't an issue for 3-chip DLP projectors because each primary color has its own dedicated image chip, so no color wheel is needed.
In video terms, resolution refers to the amount of picture detail provided by a video signal or display. Although you may hear references to "lines of resolution," that's mainly a holdover from the tube-TV era. Today's digital TVs create their images using a grid of pixels; more pixels generally equals higher resolution. This grid has a fixed number of pixels, which means if the TV receives any video signal with a different resolution, the TV will scale that signal to fit the screen's pixels.
The picture quality you see on your TV depends on two factors: the resolution of the TV's screen and the resolution of the video signal. Since video images are always rectangle-shaped, there is both horizontal resolution and vertical resolution to consider.
- Vertical resolution: The number of horizontal lines (or pixels) that can be resolved from the top of an image to the bottom. (Think of hundreds of horizontal lines or dots stacked on top of one another.) The vertical resolution of the analog NTSC TV standard is 525 lines. But some lines are used to carry other data like closed-captioning text, test signals, etc., so we end up with about 480 lines in the final image. So, all of the typical NTSC sources — VHS VCRs, cable and over-the-air broadcast TV (analog), non-HD digital satellite TV, DVD players, camcorders, etc. — have vertical resolution of 480 lines. DTV (Digital Television) signals have vertical resolution that ranges from 480 pixels for SDTV, to 720 or 1080 pixels for true HDTV. If you're comparing TVs or video sources, vertical resolution is what's usually listed: 480p, 720p, 1080p, etc.
- Horizontal resolution: The number of vertical lines (or pixels) that can be resolved from one side of an image to the other. Horizontal resolution is a slightly trickier concept, at least for analog video, because while the vertical resolution of all analog video sources is the same (480 lines), the horizontal resolution varies according to the source. Some common examples: VHS VCRs (240 lines), analog TV broadcasts (330 lines), non-HDTV digital satellite TV (up to 380 lines), and DVD players (540 lines). DTV signals have horizontal resolution that ranges from 640 pixels for SDTV, to 1280 pixels (for 720p HDTV) or 1920 pixels (for 1080i and 1080p HDTV).
Multiplying the horizontal resolution by the vertical resolution gives you the total screen resolution. For example, a 1080p screen has 1920 horizontal pixels by 1080 vertical pixels — 1920 x 1080 = 2,073,600 pixels. For an in-depth look at high-definition video resolution, see our article about resolution, or check out our video explaining what resolution numbers mean.
RF (radio frequency) jack
Sometimes referred to as a "75-ohm coaxial" connection, this kind of jack is commonly used for bringing signals from antennas and other sources outside the home to components with some type of tuner, such as TVs and TV tuners, cable boxes, DVRs, satellite receivers, etc. A 75-ohm coaxial cable can carry video and stereo audio information simultaneously. However, as a way of making a video connection between components, RF is inferior to composite, S-video, component video, and HDMI. RF cable connectors (often called "F-type" connectors) either screw onto the 75-ohm jack, or just push on to connect. See our connections glossary for more info.
There are different types of coaxial cable. Standard coaxial cable is stamped "RG-59"; higher-quality "RG-6" cable features better shielding, and exhibits less high-frequency loss over longer runs. (For connecting DBS satellite systems, it's important to use RG-6 cable to correctly pass the entirety of the digital signal.)
Circuitry that converts a video signal to a resolution other than its original format. Scaling can involve upconversion or downconversion, and may also include a conversion between interlaced- and progressive-scan formats. A scaler can be built into a TV, HDTV tuner, DVD player, or home theater receiver, or may be a standalone component.
On CRT-based TVs, the number of scanning lines measures the screen's resolution. Scanning refers to an electron gun tracing horizontal lines across a phosphor-coated screen, painting each video frame as a series of lines. Although you may still hear the term "scan lines" used when describing digital TVs that use plasma, LCD, or other pixel-based technologies, it's not really accurate. These newer TV types flash each complete screen image simultaneously without any type of actual scanning.
SDTV (Standard-Definition Television)
SDTV refers to the non-high-definition formats in the ATSC digital television standard. SDTV pictures can have either 4:3 or 16:9 aspect ratio. Picture and sound is clearer than analog NTSC video, with picture resolution of 480i or 480p. These digital signals require less bandwidth than analog signals, allowing TV stations to simultaneously broadcast multiple channels of programming in place of a single analog channel; this is called "multicasting."
Set-top box (STB)
Also called converter boxes, these receivers convert broadcasts (either over-the-air broadcast HDTV, analog cable, digital cable, satellite, or Internet-based IPTV) for display on a television.
|S-video connections are better than composite video, but aren't as good as HD-capable connections like component video and HDMI.|
Smart TVs offer the same kinds of movie and music services as Internet-ready TVs — such as Netflix® and Pandora® — and add an Internet browser, so you have full Internet access.
This 4-pin connector has rapidly been phased out of most TVs, receivers, and disc players over the past few years. S-video provides a good picture by transmitting the chrominance and luminance portions of a video signal separately. The signals can then be processed separately, reducing interference. Direct S-video connections generally outperform composite connections when hooking up video components that don't have component video or HDMI, like an old DVD player. However, they don't look as sharp as HD-capable connections like component video, and HDMI. See our connections glossary or our article about connecting your HDTV for more info.
Ultra High Definition TV
Refers to digital displays and video formats with picture resolution greater than the 1080p standard of current HDTVs. The first UHDTVs are also known as "4K" TVs because their horizontal resolution is around 4000 pixels. At the end of 2012, the first flat-panel 4K UHDTVs became available. The screens on these TVs are 3840 pixels x 2160 pixels, which is twice the horizontal and vertical resolution of 1080p (1920 x 1080 pixels). 4K has four times the total pixels of 1080p and is capable of creating a much more detailed picture. As of this writing (12/12) there is no true 4K content available, although 4K TVs include video processing that upconverts lower-resolution sources to 4K. Prototypes of "8K" UHDTVs, with 7680 x 4320-pixel resolution have been demonstrated at technology shows, but any real-world application is years away.
The term used to describe the conversion of a lower resolution to an apparently higher one. This process increases the number of pixels and/or frame rate and/or scanning format used to represent an image by interpolating existing pixels to create new ones at closer spacing.
Several years ago the FCC (Federal Communications Commission) began requiring that TVs include "V-Chip" technology to block the display of television programs based on their rating. All sets with screens 13 inches or larger manufactured after January 1, 2000 must include the V-Chip. Broadcasters are required to encode an electronic signal in TV programs indicating the level of violence, language, and sexual content. Parents can program the TV with a rating so that when the the V-Chip reads a show's signal, it will prevent it from displaying if it is above the rating.
The rating system, known as "TV Parental Guidelines," was established by the National Association of Broadcasters, the National Cable Television Association and the Motion Picture Association of America. These ratings display on the TV screen for the first 15 seconds of rated programs.
|Even though many of today's TVs have wide viewing angles, they all look better when they're viewed straight on. That's why it's handy to have a TV with a swivel base, or a wall mount capable of tilting and swiveling.|
Measures a video display's maximum usable viewing range from the center of the screen, with 180° being the theoretical maximum. Most often, the horizontal (side to side) viewing angle is listed, but sometimes both horizontal and vertical viewing angles are provided. For most home theater setups, horizontal viewing angle is more critical.
A short-range wireless technology that allows devices to connect to and transfer information over a local area network. Nearly all current Internet-ready TVs have Wi-Fi capability built-in; those that don't may still be able to connect wirelessly using an optional USB adapter.
x.v.Color (xvYCC color space)
A high-definition video color space that is supported by many HDTVs beginning in 2007 (generally models with HDMI v1.3 or newer inputs). The x.v.Color standard supports 1.8 times as many colors as the ATSC HDTV standard. Although there are HD camcorders that support x.v.Color, there are no broadcast or packaged consumer high-def sources that support it. Even if both your HDTV and high-def player support x.v.Color, your video source must be encoded with it as well or you won't see the wider color range.