4K, also known as ultra HD, is the biggest thing in TV nowadays — literally. This format offers four times the pixels of HDTV, plus better color, and is designed especially for very large TVs. That said, manufacturers are building 4K resolution into smaller sets, currently down to about 40 inches. The format is also available on laptops and desktop monitors.
The amount of content, however, is not growing as fast as the number of screens. That doesn't mean there's no use for the new sets: All 4K TVs upscale regular HD content for an ultra-HD viewing experience. To sweeten the deal, makers of 4K TVs are also equipping some of the latest sets with wider color gamuts and the ability to display a high dynamic range that prevents the highlights in bright images from washing out.
Let's look at how 4K works today and what you can expect in the future.
What Does 4K Mean?
The term 4K is derived from the movie industry format of 4096 x 2160 pixels, and refers to the roughly 4,000 pixels across the screen. That's a break from the past, in which screens were defined by the number of pixels, or lines of pixels, from top to bottom. Entry-level HDTVs, for example, have 720 lines, known as 720p, and the best HDTVs today have 1080 lines (1080p).
What Is Ultra HD or UHD?
Consumer electronics makers use a slightly lower resolution than true 4K in their new televisions and monitors. Known as ultra HD or UHD, this format measures 3840 x 2160 pixels and is exactly four times the pixel count of full-HD 1080p TVs (which is 1920 x 1080 pixels). Because the 4K term was already well known, tech companies cover their bases by using the moniker 4K/ultra HD or 4K/UHD to refer to the 3840 x 2160 format.
What's the Benefit of 4K?
With 4K TVs, you get a lot of detail. In a cityscape, for example, you may be able to see individual windows in the buildings, and even the people on the ground walking in and out of the skyscrapers. You may not necessarily want to see every pore on Kevin Spacey's face in House of Cards, but with 4K/UHD, you can now make out the faces of people in the background. Even with HD content, a 4K TV with good up-conversion capability can fill in additional detail.
MORE: Best 4K/Ultra HD TVs
4K/UHD technology results in smaller pixels compared to HD screens of the same size, so you can sit about twice as close before you see the grid of individual pixels. That's important for very large screens, whose pixels would be comparatively huge at 1080p resolution. The Consumer Electronics Association estimates that in 2016, almost all TVs over 50 inches will have 4K/UHD resolution.
The addition of wide color gamut and high dynamic range (see below) provides further benefits, though currently only a smattering of very expensive 4K/UHD sets have these capabilities.
How Expensive are 4K TVs?
The first 4K/UHD TVs were very large and very expensive, such as an 84-inch Sony model priced at $25,000 in 2013. Costs have been dropping quickly since then, with several models now priced below $1,000. But beware of very cheap 4K/UHD TVs. Upscaling HD content is still the most important function of a 4K TV, and budget models may not use the best image-processing chips to do so.
What Are the Best Sources of 4K/UHD Content?
Many major movies and some TV shows are now shot on 4K cameras, but most of this video is squished down to HD resolution before it gets to you. In the reverse of what happened with the introduction of HDTV, 4K/UHD is starting first with online services, then going to discs, and finally coming to cable and satellite TV.
Both Amazon Prime Instant Video and Netflix now shoot and stream their original programs, such as Mozart in the Jungle and House of Cards, in 4K/UHD. (You can find Netflix's UHD content with a simple search.) Amazon is also streaming some programs in HDR. Those two services, along with others such as M-Go, UltraFlix and Toon Goggles, offer 4K/UHD content from other sources — including Sony Pictures, Warner Bros., Lionsgate, 20th Century Fox and Discovery. YouTube and Vimeo also offer UHD streams.
In all these cases, you'll need a fast broadband connection of about 15 Mbps to ensure good quality. None of the major streaming players, such as Roku or Apple TV, currently support 4K, but Nvidia's Shield Android TV box does. For the most part, streaming currently requires apps running on 4K/UHD smart TVs.
Sony has been most aggressive in promoting 4K/UHD. The company sells a $700 player that downloads 4K movies and TVs shows from Sony's studio, Sony Pictures, including shows such as American Hustle and Breaking Bad. These can play on any 4K TV (not just Sony's). About 300 titles are available, but that's counting every episode of a show, such as The Blacklist, as a title. Films cost around $30 to buy and $8 to rent (for 24 hours), and are about 40GB in size; television episodes are available to purchase at $4 each.
Samsung offers its own media player with a sampling of titles from 20th Century Fox and Paramount, among others.
In 2015, the Blu-ray Disc Association announced that it had developed discs with greater capacity and finalized a format for UHD resolution, wide color gamut and HDR content. It remains to be seen which studios, if any, will produce Ultra HD Blu-ray discs (as they are formally known), and when. Consumer electronics companies like LG and Sony have been cagey about plans to make Ultra HD Blu-ray players, simply saying that they are evaluating the technology.
Cable and Satellite TV
Several pay-TV providers are beginning to offer some on-demand 4K/UHD content. Dish Network will offer a set-top box called the 4K Joey that downloads programs from the company's satellite broadcasts. Comcast provides an app for Samsung TVs and will offer a set-top box for its Xfinity customers with any brand of 4K/UHD TV in 2015.
Live broadcasts of 4K/UHD TV are probably a while off, simply because there isn't enough content to fill a channel lineup. But broadcasters such as Comcast say they will be able to handle broadcasts when the TV networks are ready.
4K games are rare, and the top consoles — PlayStation 4 and Xbox One — aren't powerful enough to support such content. But well-appointed PCs with multiple graphics cards can run some games at 4K/UHD resolution and at playable frame rates of about 30 fps, and sometimes higher. Still, 4K/UHD gaming has a long way to go before it’s a common capability, even on gaming-focussed PCs.
Your own 4K videos
4K/UHD video is migrating from professional cameras to consumer models. High-end smartphone cameras such as the Samsung Galaxy S5 and S6, the OnePlus One, and the LG G4 record in 4K/UHD. The capability is also coming to advanced compact cameras such as the Sony RX100 IV and the Panasonic LX100. Higher-end cameras are going higher res, with several mirrorless models such as the Panasonic GH4, Samsung NX1, Sony a7R II and Canon EOS-1D C DSLR. Some of these cameras shoot both Ultra HD (3840 x 2160) and true 4K (4096 x 2160).
Action cameras are also going higher-res, such as the GoPro HERO4 Black Edition and the Sony X1000V. GoPro even offers its own "channel" via a smart-TV app to show off the best action footage from GoPro users in both HD and UHD.
What Specs Do I Need to Know to Buy a 4K/UHD TV?
4K TVs started coming out before all the standards had been set. If you buy a TV (or monitor) made in 2015 or later, you should have all you need for ultra-high-def resolution, but you may not get the wide color gamut and high dynamic range capabilities. Here are the key specs you need to look for when buying.
HEVC/H.265: High Efficiency Video Coding, also known as HEVC or H.265, is the de-facto compression standard for squeezing 4K/UHD video into a stream or onto a hard drive or Blu-ray. Any new TV or monitor should support HEVC.
VP9: YouTube's alternative to HEVC is used for most 4K/UHD streams on the video service. Any 4K/UHD TV with a YouTube app supports VP9 (as well as HEVC).
HDMI 2.0: The latest standard for combination digital-video/audio connections supports 4K/UHD at up to 60 frames per second, as well as the latest wide color gamut standard. Older 4K/UHD TVs may not have the latest HDMI support, meaning they are limited to 30fps video. Virtually no 4K/UHD content currently supports the higher specs, but it's best to get a set with HDMI 2.0 so you are prepared for the future.
HDCP 2.2: Aside from videos you shoot yourself, most 4K/UHD content is copy protected using High-bandwidth Digital Content Protection (HDCP). If any of your devices don't support HDCP 2.2, they won't play premium 4K video. HDCP 2.2 is more or less standard on new 4K/UHD TVs, but only a few A/V receivers and soundbar speakers support it. If you plan to pass your video through one of these devices on the way to the TV, make sure they support HDCP 2.2, as well as HDMI 2.0.
Nanocrystals and quantum dots: These materials convert some of the deep-blue light from new LEDs into very saturated reds and greens. Combining the three colors yields a wide color gamut. Some TV makers are able to achieve a wide gamut by reconfiguring the LEDs themselves, without using nanocrystals or quantum dots.
OLED: Organic light-emitting diode screens are an expensive alternative to LCDs and don't require a backlight. The OLED material itself glows when charged with electricity and goes completely black when turned off. This allows OLED TVs, such as the LG 55EC9300 ($2,499), to produce very dark shades and high dynamic range. These screens also produce a wide color gamut.
What Is Wide Color Gamut?
The range of colors a screen can reproduce is called its color gamut. For decades, TVs have used a fairly narrow gamut that was developed for tube televisions and that leaves out deep reds, greens and blues (the primary colors that are mixed to make every other color on the screen).
Wide-gamut televisions use new technologies such as better LED backlights, color-enhancing filters or even lasers to reproduce more of the real world's colors. Some 4K/UHD TVs released in 2015 support a wide color gamut, which is roughly the same as what you get in the best digital movie theaters. As with 4K resolution, wide-gamut content is rare, but wide-gamut TVs can analyze regular video and enhance the colors to make images look more lifelike.
What Is HDR – High Dynamic Range?
Dynamic range is the span of brightness from true black to true white that a camera can capture or a screen can display. The best digital cinema cameras have a dynamic range as good as the human eye's, but screens have lagged. New screen technologies such as organic light-emitting diodes (OLEDs) and LCD TVs with full arrays of individually modulated backlights produce a better dynamic range than traditional screens and projectors can.
Known as high dynamic range or HDR, this capability shows more detail in very dark and very bright parts of a scene that, in the past, would have been simply black or totally white, respectively. Some services such as Amazon Prime Instant Video are starting to stream HDR content.
What Is 8K?
While 4K is still emerging, 8K is already looming, and several TV manufacturers have demonstrated 8K prototype sets. All the problems of delivering 4K to a TV become that much harder when you're trying to provide enough detail to fill 8K television's 7680 x 4320 pixels.
However, it may be worth it. Research by Japanese broadcaster NHK suggests that 8K resolution is the point at which it's hard for people to distinguish video from reality. It may prove to be TV nirvana.
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