Three-Minute Tech: HDTV terms
[In our Three-Minute Tech series, we tell you everything you really need to know about a technology in three minutes or less.]
Kicking back on the couch to watch a game, enjoy a movie, or lose yourself in the latest episode of Game of Thrones is a great way to relax. However, shopping for an HDTV can be baffling. LED or plasma? 120Hz or 240Hz? HDTV specs are as numerous as they are confusing, but here’s what a few of the most-common terms mean.
For more info, check out PCWorld’s HDTV buying guide.
720p, 1080p, and “Full HD”
These numbers refer to the lines of resolution of a TV’s screen. 720 means 1280-by-720 pixels, and 1080 equals 1920-by-1080 pixels. The p after the number indicates that it supports progressive scanning, wherein the lines of each frame are drawn in sequence on your screen. With i or interlaced signals, the odd lines and even lines in the picture showcase successive frames. You’ll likely see a sharper image with a progressive scan, especially if you pause the video.
You may see lots of marketing materials that use the phrase “Full HD”, which simply means the TV supports 1080p video.
1080p is standard on larger HDTVs these days, but some smaller sets—ones with screen sizes up to 32 inches—often come with 1366-by-768-pixel displays, very close to 720p. Broadcast and cable TV shows are generally delivered at 720p or 1080i, while Blu-ray discs, games, and some downloaded and on-demand movies offer 1080p resolution.
60Hz, 120Hz, 240Hz, 600Hz
The Hertz (Hz) number you see in HDTV specs refers to the refresh (redraw) rate. For LCD-based HDTVs, those numbers are 60Hz, 120Hz, 240Hz, and sometimes even 480Hz. At 60Hz (the standard refresh rate), the screen refreshes 60 times per second. At 120Hz and 240Hz, your TV redraws the image on the screen more often, which can help reduce blurring in fast-motion scenes.
Those higher rates also work better when viewing films shot at 24 frames per second, because 24 divides nicely into 120 and 240, but not so much with 60. Higher refresh rates are also beneficial with 3D content. In general, the difference between 60Hz and 120Hz is huge, while the jump from 120Hz to 240Hz isn’t as noticeable for most people.
For plasma TVs, you’ll sometimes see a “sub-field drive” listed as 600Hz. This isn’t the same as a refresh rate on an LCD TV; 600Hz means the plasma display processes 10 interpolated pictures per frame, which purportedly makes fast motion appear smooth.
LCD vs. LED vs. plasma vs. OLED
These terms refer to the display technology. As explained in PCWorld's buying guide, LCD, or liquid crystal display, uses a backlight that shines through a layer of liquid crystals, which move to transmit or block the light. LED TVs are simply LCDs that use light-emitting diodes (LEDs) as the source of the backlight. Compared to LCD TVs, LED TVs are often more energy-efficient, but they’re also more expensive.
Plasma TVs use an electrical charge to make a gas give off ultraviolet light, which in turn causes phosphors to glow—the same process as a fluorescent lamp, basically. Compared to LED TVs, plasma sets are usually much cheaper at bigger sizes, show deeper black levels and contrast, and do a bit better with fast motion. However, due to the lack of backlight, plasma TVs usually need a darker room to look their best.
OLED (organic light-emitting diode) may sound like “LED,” but it’s a different beast altogether. OLED sets don’t require backlighting, as each pixel emits its own light (or emits no light at all). As a result, OLED sets are very thin, very impressive in terms of deep blacks and contrast, and they’re very expensive. They’re also not available yet, but they’re coming soon.
HDMI, or High-Definition Multimedia Interface, is the standard connection type for digital content. It carries both digital video and multi-channel digital audio over a single cable, and it’s found on every new TV and on the back of most Blu-ray players, cable/satellite boxes, DVRs, game consoles, and set-top boxes from Apple and Roku. It’s good to have several HDMI ports on your TV, but HDMI switches—both standalone and built into lots of today’s AV receivers—can help if you don’t.
These days, many TVs have the ability to connect the Internet, either via a wired ethernet port or with built-in Wi-Fi. These are typically called Smart TVs. The services they offer vary, but they usually include paid video sites such as Netflix and Hulu Plus; apps such as Facebook, Twitter, and YouTube; audio services such as Pandora and SiriusXM; and widgets for sports scores and weather.
More and more new TVs are being designated as 3D-ready. Such TVs play everything a normal “2D” TV does, but they can also display a 3D movie playing on a 3D Blu-ray player or coming from a cable or satellite provider. To enjoy any of that content, you’ll still need to wear 3D glasses: Either active shutter or passive (polarized) specs, depending on the TV.
My three minutes are up
You can get pretty far down the rabbit hole when talking about HDTV specs, but those are the basics. If you’d like to learn more about that mysterious specs lurking in your prospective TV’s marketing materials, here are some useful additional resources from PCWorld.