What is a 4K TV and why buy one?

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What is a 4K TV?

4K, as you’ve probably guessed, is short for 4,000. To be exact, images that are 4K in quality measure 4,096 by 2,160 pixels in resolution. By comparison, a Full HD picture measures only only 1920 by 1080 pixels, so a 4K TV actually offers four times better image quality than a Full HD television. And it's even better still than an HD Ready TV (you can find out more about the differences between the two in our HD Ready vs Full HD explainer).

4K televisions offer you an image of such depth and clarity that to actually see one for the first time can be a pretty breath-taking experience, and returning to HD television afterwards is kind of like coming back to Kansas after visiting Oz.

You’ll often hear the terms ‘Ultra HD’, ‘UHD’ and ‘4K Ultra HD’ - ultimately, they all refer to the same technology. That said, 4K and Ultra HD images are not quite the same, since they have different aspect ratios. A 4K cinema screen will have a resolution of 4,096 by 2,160 pixels; a home television has 3,840 by 2,160 pixels.

Yes, that’s technically less than 4K in width. So why is the phrase ‘4K’ used? Being honest, it’s simply because it falls off the tongue more easily: it’s textbook tech jargon. Some TV makers only use the phrase Ultra HD, but in practical terms, it’s completely interchangeable with 4K.

Why buy a 4K TV?

There’s that gorgeous, ultra-crisp picture quality of course. But let’s assume for a minute that cutting-edge screen quality isn’t your priority, and you’re more focused on spending your money sensibly.

If you’re in the market for a new TV, you’ll be hard-pressed not to buy a 4K set. It’s more or less becoming the absolute standard for most TV manufacturers. There are exceptions to this: if you’re looking for a smaller set, like a 32-incher for your kitchen counter perhaps, then you’ll often find these are still just Full HD. That’s because a screen of this size simply doesn’t need to feature the 8-plus million pixels of Ultra HD television - your eyes won’t appreciate them. (For more information about choosing the right-size TV for your viewing space, you can read our What size TV should I buy? article.

But for TV sets of 40-inch and larger, short of going to a second-hand appliance store, you’re going to struggle to find any non-4K sets made in the last few years. Oh, and if you’re wondering when 4K itself will go the way of Full HD, Standard Definition and cathode rays, it’s already happening - you’ll already see 8K sets on the market. But these are prohibitively expensive, and the technology only really shines on enormous 75-inch to 85-inch sets. So breathe easy: you’re fine with 4K for now.

You may have already thought: ‘It’s one thing to have a 4K TV, but what content can I watch in 4K?’ If so, you’ll be pleased to hear that all the major streaming platforms deliver 4K content to 4K-ready screens. Netflix, Amazon Prime Video, YouTube, Hulu all deliver 4K content, while Apple and Google both offer 4K downloads. BBC’s iPlayer has dipped a toe into 4K, offering certain content in Ultra HD, and will doubtless offer more and more in the future.

One thing you should keep in mind, though, is that streaming 4K content uses up a considerable amount of your internet bandwidth - around 25Mbps. If you're not sure whether your current broadband is suitable for 4K streaming, make sure you read our what broadband speed do I need article.

What to look for when buying a 4K TV

If you’re buying a 4K TV, then you can reassure yourself that any 4K content you watch will be of a certain quality. But not all 4K TVs are created equally: here’s where things get a little more complicated.

HDR

With a 4K television, you know you’ll have those 8 million-odd pixels in front of you. But how good they are presented is dependent on the television’s HDR, or High Dynamic Range. HDR is a type of technology that ensures there’s a strong contrast between the bright and dark pixels in the image, and that there’s an ample range of colour. Ultimately, it’s about getting those pixels to mimic actual reality as accurately as possible.

Right now, there are a number of different HDR formats. You’ll encounter names like HDR10, Dolby Vision, HLG, HDR10+, and Advanced HDR by Technicolor. Our advice is to not to get too hung up about HDR when buying a 4K TV, no matter how much the manufacturers might be championing whichever formats their television supports. For example, Netflix fans can keep an eye out for Dolby Vision, which the streaming service supports - but it shouldn’t be the deciding factor.

QLED and OLED

By contrast, OLED and QLED technology is something that does make a difference - most notably in the accompanying price tag. Why, you may ask, does the Samsung 55-inch TU7100 4K TV cost £529 on Amazon, while the Samsung 55-inch Q95T QLED 4K TV cost £1,134? Both TVs are the same size; both are 4K. Why the price difference?

Because the latter is a flagship television that showcases the brand’s illustrious QLED technology. QLED makes use of ‘quantum dots’ that replace LCD’s liquid crystals. We’ll spare you the hard science, but to summarise, these little dots emit their own light, and make a tremendous contribution to the contrast and colour levels of the TV screen.

However, QLED technology is exclusively that of Samsung. Another type of image tech you’ll see elsewhere is OLED. This stands for Organic Light Emitting Diode, which work a similar magic on the black levels, contrast and refresh rate of whatever you’re watching - you can get into details in our what is an OLED TV explainer. You’ll find OLED screen in high-end TVs from all major brands - all except Samsung.

OLED televisions typically cost on the far side of £1,000, with larger flagships models costing two or even three times as much. QLEDs are a little cheaper, but not cheap: they start at around £750 to £800. To find about more about these televisions, make sure you read our What is QLED article.

You might also want to look at LG's Nanocell range, which use a different technology to QLEDs but to similar sub-OLED result. Read our What is a Nanocell TV explainer for more about these LG TVs.

Which brands make the best 4K TVs?

Given that it’s fast becoming standard, you could easily just ask the question, ‘Which brands make the best 4K TVs?’ We can tell you that television’s market leaders are Samsung, LG and Sony, and any television you buy from their lines will offer you a reliable 4K-watching experience.

Samsung’s televisions use Tizen, the brand’s own smart platform which has won accolades for its ease of use. As we mentioned, the higher-end models make use of QLED technology that will ensure whatever 4K content you’re watching is completely optimised. Take a look at the Samsung 55-inch 4K Q95T for an example of one of the brand’s QLED 4K sets.

LG televisions, too, are some of the best available 4K televisions to buy. The WebOS smart platforms the brand’s 4K sets is seen by many as the very best out there; take a look at the LG 55-inch CX 4K TV for an example of a top-end set with that gorgeous OLED tech.

Sony’s 4K televisions, too, will offer you a smooth experience with Google’s Android TV platform that’s also highly reputed. The Bravia range has enjoyed an excellent reputation since the days that HD television was still a new-fangled thing; the Sony Bravia KD55XH81 is now light-years ahead in the picture quality it can offer.

Read our article on what is a smart TV for more info on each of these smart platforms.

Want to see what a cutting-edge 4K television looks like? Don’t miss our guide to the Sony Bravia XR A90J.