Last updated on 12/03/2010
HDTV jargon can be pretty confusing. Here's a quick and dirty glossary of some of the most common terms in the HDTV lexicon. If we're missing anything, leave a comment and we'll try to add it quickly. Feel free to suggest your own definitions too.
By Liam McCabe
Component: Refers to a type of cable and connection standard. High-definition signal. Red, green, and blue inputs. Used with Playstation 3, XBox 360, and digital cable/satellite TV boxes, among others.
Composite: Refers to a type of cable and connection standard. Red, white, and yellow inputs. Also known as A/V or RCA cables. Used with almost any source. Standard definition signal.
Connected TV: This refers to a TV that can connect to the Internet. It’s most commonly used to stream extra video content, but also for audio, news, and other “interactive” content. A few TVs even support Skype videocalling.
Contrast Ratio: Contrast ratio refers to the difference between a TV’s brightest whites and darkest blacks. In theory, a higher contrast ratio should produce a more stunning picture, but no two manufacturers measure dynamic contrast ratios the same way, so it really amounts to marketing hyperbole. If you can find it, the static contrast ratio is a much more accurate measurement.
DLP: This refers to a TV with a direct-light projection display, typically projected from the rear. They’re too deep to be considered flat panels, and because of advances in LCD and plasma technology, these sets are increasingly uncommon. The screen sizes can be enormous, so those in the market for 80+ inch TVs should look for a DLP, but most consumers can just ignore this category.
Edge lit: This refers to a type of LED TV with LEDs arranged around the edges of the display, rather than directly behind the display. This type of lighting is not as highly regarded as the local-dimming style, and on some sets it produces inconsistent lighting levels -- the lighting doesn’t reach parts of the screen as well as it does other parts, so there are dark spots. But an LED edge-lit picture still looks more vibrant than a fluorescent one, so it’s generally worth the extra cost, and edge-lit sets are cheaper than local-dimming ones.
HDMI: Refers to a type of cable and connection standard, the High-Definition Multimedia Interface. It allows a 1080p video signal and audio signal to travel from a source to a TV over one cable. Used with Blu-ray players, Playstation 3, later XBox 360 models, digital cable/satellite TV boxes, and some digital cameras or camcorders, among others.
Interlaced: Signified with a ‘i’ as in 1080i, interlaced scanning means that every second line is refreshed during each cycle. A video source can be interlaced, and all TVs can support interlaced scanning. Interlaced TVs can display progressive content, but it’s down-converted into interlaced content. A picture from an interlaced source is not as smooth as a progressive one.
LCD: This refers to a TV with a liquid crystal display, typically backlit by a fluorescent light. Sometimes to avoid confusion with LED TVs (see below), these are referred to as conventional LCD TVs. In general, these sets offer a reasonable balance between price and performance, and are lighter, thinner and much more energy efficient than their plasma counterparts. These sets can have screens anywhere from 7 to 65 inches diagonal, and are available in a huge variety of configurations. If you buy an HDTV this holiday season, chances are that it will be an LCD.
LED: This refers to a TV with a liquid crystal display, illuminated by a light-emitting diode rather than a fluorescent lamp. These sets are even thinner, lighter, and more energy efficient than conventional LCDs, and the picture is generally more vibrant and color-accurate. These sets are also more expensive. They do come in wide variety of configurations, but the smallest sets are 32 inches, with few exceptions. Purists are quick to remind us that an LED TV would be like a jumbo-tron -- every pixel needs to be an actual light-emitting diode, but that’s not a practical design. So rather than constantly repeating the equally impractical proper name -- “LED-backlit LCD TV” -- the industry has adopted the practice of simply calling them LED TVs.
Local dimming: This refers to a type of LED TV with an array of LEDs behind the screen, rather than around the edges. The LEDs can work independently of each other, so if one section of the screen is dark (a night sky setting, for example) and another section is bright (a character holding a lantern, perhaps), the LED behind the dark area will stay relatively dark, while the LED behind the bright area will increase its brightness. It’s an impressive effect in high-contrast scenes, and even in scenes without that contrast, the backlighting is more consistent than what edge-lit sets (see below) can do. Local-dimming sets are also more energy efficient, and more expensive as well. Local-dimming LED TVs in general are the most expensive sets available.
Plasma: This refers to a TV with a plasma display, which uses noble gases, mercury, and electricity to display a picture. Plasma TVs have deeper blacks and smoother pictures than LCD and LED TVs, and inch-for-inch, they’re often cheaper than either. On the downside, they’re very heavy and consume more than twice as much power as LCDs of the same size. Also, the smallest commonly available plasmas are 40 inches, so the size selection is limited. Still, plasma TVs are the choice of videophiles worldwide and are still viable more than a decade after they came to market.
Progressive: Signified with a ‘p’ as in 1080p, progressive scanning means that every line is refreshed during each cycle. A video source can be progressive, and most TVs support progressive scanning. It’s a smoother picture than an “interlaced” source.
Refresh Rate: A TV’s refresh rate, measured in hertz, refers to how often a fresh image is displayed on the screen. A 60Hz set displays a fresh image 60 times per second, a 120Hz set does so 120 times per second, so on and so forth. In theory, faster is better because the picture will look smoother, but that’s only true up to a certain point, after which the human eye can’t really tell the difference. 120Hz seems to be the sweet spot for 2D sets, though 3D TV owners will want all the refreshing they can get.
Resolution: This refers to the number of pixels on the screen. HDTVs come in two common resolutions, 720p and 1080p, and the less common 1080i. The number refers to how many vertical lines the screen displays, and the letter refers to the type of scanning. ‘P’ stands for progressive, which means each line can be refreshed every cycle, and ‘i’ stands for interlaced, which means every second line is refreshed every cycle.
3DTV: This refers to a TV that supports stereoscopic 3D content, so that the picture looks like it has depth. Active shutter glasses are required, as is 3D content from a 3D Blu-ray or compatible cable or satellite channel. 3DTVs also support 2D content -- that is to say, using the 3D effect is an option, not a requirement. A few can convert 2D content into 3D content, but this doesn’t work very well.