What is 4K TV and Ultra HD? All you need to know about 4K

Everything you need to know about 4K and UHD

The world of TVs has moved on a lot in the last few years. There are new technologies and certifications, all aimed at helping TV tech take the next leap forward. They all carry snappy acronyms like HDR and BT.2020. The one you need to look out for is ‘4K’. There has been talk of 4K for years, but it’s no longer just something for the tech-minded early adopters. This advancement has properly hit the mainstream. It is now an important new standard.

How important? Well, the CES in Las Vegas is the world’s biggest annual tech show, and 4K TVs have dominated the show for the last few years. Netflix has been hard at work pushing 4K, with nearly all its new Originals programmes being shown in the format. Amazon Video isn’t far behind, and its Fire TV was the first media streamer to handle 4K. Then there’s Sky Q, which brings 4K to a whole new segment of mainstream TV viewers in the UK. On the gaming side, there’s 4K love from the Xbox One S and PS4 Pro.

The latest to jump onto the bandwagon is Apple, with the new Apple TV 4K. If that’s not a robust endorsement of a format, I don’t know what is.

With all that in mind, here’s crack at compiling an ultimate guide on 4K. Here are some of the most common 4K-related questions, to save you a load of time and effort when buying a new TV.

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Q: What exactly is 4K?

A: 4K, also known as Ultra HD, generally refers to a resolution of 3,840 x 2,160 pixels. That’s four times the 1,920 x 1,080 pixels found in your full HD TV. We’re looking at about 8.3 million pixels. Cramming so many pixels into a TV means a higher pixel density, and you should have a clearer, better defined picture. It’s not about sharpness, it’s about letting you see more detail and texture.

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Q: What is the difference between 4K and Ultra HD?

A: 4K is by far more commonly used, but you’ll also find people calling it Ultra HD, or UHD. For the average consumer buying a TV, these are one and the same. But there is technically a difference.

In its correct usage, true 4K refers to a resolution of 4096 x 2160, which was first introduced in digital cinemas. Meanwhile, UHD refers to a resolution of 3840 x 2160, which is what you get on the TVs you actually take home.

So technically, ‘4K’ is the wrong term for 3840 x 2160 displays and content, but it’s a mistake so common that there is no functional difference anymore. For most people, the two terms are interchangeable.

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Q: Is 4K actually any good?

A: While 4K has its detractors, we’re big fans. The extra resolution of 4K images adds better definition and clarity to the picture. The result is images that look incredibly life-like, more like looking through a window than watching TV.

4K is especially effective on very large screens – so ideally you’ll go for a 65-inch set or even bigger. That said, we’d argue that 4K resolution clearly improves picture quality at pretty much any screen size. The effect is more noticeable if you’re moving to 4K from a TV of the same size. Let’s say you have a 50-inch HD TV and you upgrade to 4K: you are cramming four times the number of pixels into the same amount of space. That makes for a noticeably denser picture with finer detail.

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Don’t just take our word for it: 4K is considered by the film-making community as being able to reproduce the sort of resolution and ‘finish’ you get with 35mm film.

There is a some talk now about 8K, but right now that’s limited to super-sized TVs over 70 inches. And there’s no content.  That’s overkill, and this standard won’t attain mainstream acceptance (or affordability) any time soon. You’re safe to go ahead with your 4K TV purchase.


Q: Do I need to sit nearer my TV to benefit from 4K?

A: To get the best from 4K, it is recommended that you sit closer to your screen than you would with with HD TVs. The extra resolution and increased pixel density means you can sit further forward without spotting individual pixels. And filling up  more of your field of view makes for a more immersive experience.

There are ‘scientific’ charts in circulation suggesting that you must sit extremely close to appreciate the extra resolution at all. While we’d agree sitting close gives you the most impact, we reject the notion that you get no benefit at all from more distant viewing positions. Lines are still more cleanly drawn, you still perceive more depth, colours still look more subtly and smoothly rendered, and objects within the picture still look more solid and three-dimensional.

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4K packs in four times the number of pixels as Full HD / 1080p.

Q: Is a 4K TV all I need to start watching 4K?

A: No. While your 4K TV will use processing to upscale HD and standard definition pictures to its 4K pixel count, you will still want a native 4K source. Examples include 4K streaming services like Netflix and Amazon, as well as Ultra HD Blu-ray players.

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Q: What 4K content can I watch?

A: A few years ago, the short answer to this was ‘not a lot’. Then answer became ‘not a lot but there’s more coming soon’. Now there is plenty of 4K content.

The most important 4K option is Netflix. The subscription on-demand service currently carries a growing library of TV series and films you can stream in 4K for £8.99 per month (up from £5.99). In terms of TV, Breaking Bad and House of Cards have been joined by the likes of Marco Polo and The Blacklist. UHD films include The Amazing Spider-Man, Crouching Tiger Hidden Dragon and Jerry Maguire, among others. You also get a few nature documentaries.

Amazon Prime Instant Video also offers some 4K content free of charge, including original Amazon series Mozart in the Jungle, Extant, and Transparent,

Otherwise your main source of 4K content is the internet, predominantly via YouTube and a handful of dedicated 4K sites such as hd-trailers.net and demo-uhd3d.com. You can download files from these, transfer them to USB drive, and play them directly into your TV (so long as your TV is compatible with the video encoding format of the clip you want to watch).

BT has also has a 4K channel BT Sport Ultra HD. As the name suggests, this is a sports channel (read further down for more information about sports) and it shows Premier League, FA Cup and Champions League football along with Aviva Premiership rugby. You’ll need one of BT’s Ultra-HD boxes to take advantage of the service though.

Finally, Sky’s Sky Q Silver box and Sky Q service, which has added 4K content since launch. You can watch many films and TV shows in 4K, while most Premier League football games are broadcast in 4K now.

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Q: Do all 4K TVs support 4K streaming?

A: These days, yes. The first 4K TVs out in 2013 couldn’t handle Netflix 4K streams, as Netflix adopted the HEVC video format and none of the TVs out then could decode it. These days, you’ll struggle to find any 4K TV in a shop that cannot stream 4K.

Q: What broadband speed do you need to stream 4K?

A: Netflix and Amazon are the big names streaming 4K, and both services need a minimum of 15Mbps to do 4K. And your speeds need to remain consistently at or above that figure. As soon as you drop lower – due to high contention rates at peak usage times, say – the picture will slip back into HD mode. And don’t worry if you start off with a blurry image: it’s quite common for streaming services to start a programme at a low resolution and then bump it up to HD and UHD after the initial buffer.

To try and cover itself for this eventuality, Netflix actually says on its website that you need 25Mbps minimum. But we’ve confirmed with Netflix that a consistent 15Mbps is enough. It’s worth bearing in mind that this means you need 15 to 25Mbps of spare bandwidth, so if someone else is using your Wi-Fi, you’ll need to have that amount of bandwidth free after you account for the other person’s usage.

Compression techniques improve all the time, so it’s possible you may in the future need slightly lower broadband speed to experience 4K on Netflix or other rival 4K streaming platforms. But bear in mind that high levels of compression inevitably negatively affect picture quality, so if you’re serious about 4K a fast broadband connection is a must.

Q: What is UHD Blu-ray?

A: We’ve got a detailed breakdown of UHD Blu-ray which you can check out for a full rundown of the new format. In short, Ultra HD Blu-ray discs have a much larger capacity than standard Blu-ray discs, and as such can carry the information needed to store 4K video without the compression of streaming sites. Basically, the best form of 4K you can watch at home.

There are plenty of UHD Blu-ray players out now, including the Panasonic DMP-UB900 and Sony UBP-X800. Microsoft provides an affordable alternative in the Xbox One S, which plays 4K Blu-rays alongside games.

Q: What connections do I need to watch 4K?

A: We’d love to say ‘an HDMI socket’ and leave it at that, but wouldn’t you know it, it’s just not that simple.

The issue here is that not all HDMI sockets are equal. There have been multiple versions/standards of HDMI since the digital connection first appeared, with the latest v2.0 HDMI specification being defined specifically with 4K feeds in mind.

The most significant advantage of v2.0 HDMIs from a 4K perspective is that they support increased data bandwidth, and so enable playback of 4K feeds with full (so-called 4:4:4) colour sampling at frame rates of up to 60fps. The previous v1.4 HDMIs only support 4K feeds up to 30fps.

Most of the major 4K TV brands now carry HDMI 2.0 in their current TVs – LG, Sony, Panasonic and Samsung are all onboard with it now, as is Philips.

Related: HDR TV: What is it and why should you care?

Q: Can I make my own 4K content?

A: Indeed you can. There are now domestic cameras out there capable of producing startlingly good 4K quality without costing the earth. Two of the best examples are the £1,500 Sony FDR-AX100 camcorder and the similarly priced (with lens) Panasonic DMC-GH4 camera.

Many modern smartphones are also capable of capturing 4K video, including Apple’s iPhone 8 and iPhone X. Of course, 4K recording has long been supported at the top end of the Android market, and 4K video capture is present on current flagships such as the Samsung Galaxy S8, HTC One U11, and the LG V30.