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What you need to know about 4K TVs

Curious about Ultra HD, also known as "4K"? Here's a cheat sheet.

Geoffrey Morrison Contributor
Geoffrey Morrison is a writer/photographer about tech and travel for CNET, The New York Times, and other web and print publications. He's also the Editor-at-Large for The Wirecutter. He has written for Sound&Vision magazine, Home Theater magazine, and was the Editor-in-Chief of Home Entertainment magazine. He is NIST and ISF trained, and has a degree in Television/Radio from Ithaca College. His bestselling novel, Undersea, and its sequel, Undersea Atrophia, are available in paperback and digitally on Amazon. He spends most of the year as a digital nomad, living and working while traveling around the world. You can follow his travels at BaldNomad.com and on his YouTube channel.
Geoffrey Morrison
5 min read
Andrew Hoyle/CNET

Ultra HD, colloquially known as "4K," is everywhere on TV shelves and online this year. Previously restricted to only high-end models, 4K resolution has become so inexpensive that your next 50-inch or larger TV will probably be 4K.

What does it mean? Does it matter? Why should I care?

Here are the basics -- a cheat sheet if you will -- about this advancement in TV technology.

Higher than HD resolution, and possibly more

To put it simply, Ultra HD is a resolution greater than HD. Resolution on TV screens consists of physical pixels, the tiny dots of light that together form the picture. Look closely (you may need a magnifying glass) and you can see them, but move back to a typical seating distance and they blend together.

Today's 4K TVs almost all have a horizontal resolution of 3,840 pixels and a vertical resolution of 2,160 pixels. A single line of pixels across the screen is 3,840 pixels long, and a line of pixels down the screen is 2,160 pixels long. Multiply those numbers and you end up with more than 8 million, which sounds great when you're trying to sell a new TV.

That's four times as many pixels as most current and older HDTVs with 1080p resolution. Ultra HD also includes cinema 4K (4,096x2,160 pixels) and future resolutions like "8K," or 7,680x4,320.

But for right now, 3,840x2,160 is what matters. If you want to dive in more, check out: TV resolution confusion: 1080p, 2K, UHD, 4K, 8K, and what they all mean.

Enlarge Image

Four resolutions compared: standard definition; full high definition; and the two kinds of ultra high definition (Quad HD and 4Kx2K).


Ultra HD is almost entirely just about this increase in resolution. Resolution is just one part of a good picture, however, and not the most important. What's far more interesting is high dynamic range, or HDR, which we'll get to in the next section.

Can you even see the difference?

Probably not. There's only so much detail the human eye can resolve. If you have 20/20 vision (which is common), sit about 10 feet from your TV (also common), and are buying a typical TV (50 inches or so), you're not going to see the additional resolution. Check out Chris Heinonen's excellent 4K Calculator to see if you can benefit from the extra resolution.

That said, it doesn't matter that much. The prices have fallen so quickly that if you want a mid- to high-end TV, it's going to be 4K.

Watch this: What is 4K?

As mentioned above, HDR is the latest tech advancement, and it's really cool. It means a better contrast ratio and richer colors for a more realistic image. Check out how HDR works for more info. All 2016 high-end TVs are also HDR-compatible.

'Ultra HD' vs '4K'

The official industry moniker for this new resolution is Ultra HD. But it's commonly referred to as "4K" or even "2160p." 4K is the cinema standard that deals with a similar resolution (generally 4,096x2160 pixels).

Most people, myself included, would rather just call it 4K. Yes, this isn't strictly accurate, but I'm not nearly pedantic enough to care. Some are. Also, 4K is easier to type and say.

For the record the Consumer Electronics Association, the closest the US TV industry has to an authority in this matter, sees "4K Ultra HD" as a "legitimate use" in line with its guidelines. That catchall term, or some variation thereof, appears to be what most TV makers are using, at least for now.


The Samsung UBD-K8500 4K Blu-ray player.

Sarah Tew/CNET

Do you need new 4K equipment?

To actually watch 4K TV shows and movies on your new 4K TV, you will need a 4K source. Most 4K TVs have such a source built in already, in the form of smart TV streaming apps -- think Netflix, YouTube and Amazon.

If you want to watch 4K beyond those apps you'll need an external source, such as a 4K Blu-ray player, a 4K media streamer or 4K video game console. Some cable boxes and the TiVo Bolt can do 4K too, but 4K broadcast TV is still very rare.

Your current HDMI cables can probably pass 4K. If there is any piece of equipment, like an AV receiver, between your source and your TV, it needs to be HDMI 2.0a. While the HDMI cable is just a dumb pipe, what you connect to it has to be "smart" enough to send the relevant data.

AV receivers with HDMI 2.0a can pass all 4K and HDR content. Older equipment was most likely HDMI 1.4, which can do certain types of 4K, but not HDR. So while your cables are probably OK, you might need to upgrade your receiver, for example.

4K HDMI cables
HDMI.org/Geoffrey Morrison/CNET

Now and the future

Like it or not, this is happening. Ultra HD displays are the future. Prices are already falling from the major manufacturers.

A big issue right now, like the early days of HD, is content. There are more and more 4K and 4K HDR TV shows and movies coming out every week, but nowhere near as much as good old HD.

For where to find 4K stuff to watch, check out: Where can I get 4K Ultra HD TV shows and movies today? Though that article is from 2015, and US-centric, the providers are still accurate (they all just have more content). If you're looking for HDR, check out: Where can I get HDR TV shows and movies for my new HDR TV? HDR content is a subset of 4K content, but it's growing very rapidly.

In the meantime any 4K TV will also display HD too, and chances are that's what you'll be watching most, at least for the next few years.

Got a question for Geoff? First, check out all the other articles he's written on topics such as why all HDMI cables are the same, LED LCD vs. OLED, why 4K TVs aren't worth it and more. Still have a question? Tweet at him @TechWriterGeoff then check out his travel photography on Instagram. He also thinks you should check out his sci-fi novel and its sequel.

Editors' note, November 8, 2016: Originally published in 2014, this article was updated with the latest information and a new headline.