4K TVs are seemingly everywhere right now, but what does 4K mean and what’s Ultra HD TV? For that matter, what’s 8K and will TV get better than this? We explain everything.
This year we’ve seen the launch of BT Sport Ultra HD, the UK’s first live 4K TV service. This is a milestone in British broadcasting history, a good teaser of what’s to come.
More recently, we’ve seen Sky unveil something called Sky Q, a new smart TV ecosystem which the satellite broadcaster has talked up as ‘the UK’s most comprehensive Ultra High Definition service’.
Put simply, 4K is coming. Here’s what it is, what you need to know and consider and what the future holds (spoiler: it’s 8K).
What is 4K Ultra HD?
Here’s the short TL;DR answer: 4K Ultra HD TV is roughly four times as detailed as 1080p Full HD.
The proposed resolution for 4K TV sets is 3840 pixels wide by 2160 pixels high, compared to 1920 wide by 1080 high - in other words that’s 8 million pixels versus 2 million pixels, four times the detail.
For an idea of how mind-blowing that will be, consider the difference between boring old standard definition and Full HD.
At this point we should clarify something for the benefit of cinema enthusiasts and pedants in the comments section. The standard 4K resolution established by the DCI (Digital Cinema Initiative) is actually a lot higher - it’s 4096 x 2160.
This is where the ‘4K’ name comes from; it's shorthand for four thousand, as in 'just over 4,000 pixels wide.'
Why is the 4K TV resolution smaller than cinema resolutions? The answer is down to content; broadcasters and TV content producers have instead adopted 3840 x 2160, also known as UHD-1, as their standard for 4K.
To be accurate, you should use ‘4K Ultra HD’ at all times when talking about 4K TV sets to avoid confusion with the DCI standard.
As it's unlikely that we’ll see 4096 x 2160 TV sets hitting the shelves, we tend to use ‘4K’, ‘4K TV’ and ‘4K Ultra HD’ interchangeably in articles and features when talking about Ultra HD services. It should hopefully be clear from the context (we're a consumer tech site, not Sight & Sound) that we’re talking about TV sets and not digital cinematography.
What can I watch in 4K Ultra HD right now?
There’s not a huge deal of 4K TV content available to consume right now.
Provided you’ve got a decent superfast broadband service, either FTTC (Fibre to the Cabinet) from an Openreach-based ISP, cable broadband from Virgin Media or, ideally, a full fat FTTP (Fibre to the Premises) from BT, Hyperoptic, CityFibre, Gigaclear or B4RN you should be able to stream 4K Ultra HD content from Netflix and Amazon’s Prime Instant Video services.
We’ve compiled guides on how to get 4K video content from both of these providers, detailing things like prices and bandwidth requirements. Generally speaking, you’ll need at least 25Mbps of spare bandwidth in order to reliably stream Ultra HD shows and movies.
Aside from Netflix and Amazon, there’s also BT Sport Ultra HD. In order to get this, you have to sign up for a superfast BT Infinity package and you’ll need to be living in an area where your connection can support Ultra HD streams.
Next year, Sky will launch Sky Q, a new satellite TV service. Details are thin on the ground right now, but the delivery of live TV channels over satellite as opposed to an Internet connection does away with the need for you to have an expensive broadband service.
That said, for the on-demand elements of Sky Q to work, you will need an Internet service.
Does the ‘Ultra HD Ready’ badge mean my TV will get all 4K channels?
You might have seen TVs sold in the high street and online with the above logo somewhere on the stand or page.
All this kitemark really means right now is that you’re buying a TV with a resolution of at least 3840 x 2160 and an HDMI 2.0 port.
It’s worth noting that the current HDMI 2.0 spec only supports 4K video at up to 60fps (frames per second). Broadcasters are less keen on using 60fps and 120fps settings for live TV, because tests have shown that this creates an unpleasant strobing effect, not helped by the flicker caused by high frequency LED floodlights - the kind typically found in football stadiums.
For this reason, it’s likely that 50fps will remain the top frame rate for 4K content until future versions of HDMI are announced.
Should broadcasters eventually decide that 100fps or 150fps is what’s really needed for slick-looking live sporting action, as Sky's chief engineer Chris Johns said in September 2014, then the HDMI 2.0 spec - and by extension the ‘Ultra HD Ready’ badge - will be redundant.
When will 4K TV channels arrive on Freeview, Virgin Media, Freesat and other platforms?
Both the BBC and Sky are co-helming the DTG UK UHD Forum, a cross-industry body that will define broadcast standards for 4K Ultra HD TV.
UK broadcasters and ISPs are currently testing out 4K transmissions across a variety of mediums right now.
The BBC has captured some incredible 600fps 4K video and collaborated with Virgin Media for a trial 4K broadcast of the 2014 Commonwealth Games. Sky has transmitted live Premier League games in 4K using its existing satellites.
At the DTG Summit 2015, broadcast equipment makers Rohde & Schwarz demonstrated a live transmission of 4K Ultra HD TV over the airwaves.
But while there’s plenty of work going on behind the scenes, there’s no set date for when we’ll see 4K TV channels arriving.
Sky recently confirmed that its forthcoming Sky Q platform would feature 4K Ultra HD content, but other than ‘later in 2016’ there’s no launch date.
What does Recombu think of 4K Ultra HD?
As we said, 4K TV is roughly four times as detailed as 1080p Full HD.
BT Sport Ultra HD’s 5.1.4 future plans sound great: Behind the scenes at the British MotoGPThat’s probably the best way, in writing, to convey how good it looks. We can throw all sorts of nice superlatives about how ‘incredible’ and ‘eye-poppingly good’ it is, but to paraphrase Martin Mull, writing about display resolutions is like dancing about architecture.
What we can say is that pictures are sharper and more richly detailed than on Full HD video, as you might expect. You start to notice little details like the eyelashes of actors and when you’re watching a football game, you start picking up on details like faces in the crowd and blades of grass on the pitch.
Put simply, if that fateful QPR vs Chelsea game back in 2011 had been broadcast in 4K, lip readers would have had less of a problem working out what John Terry said to Anton Ferdinand.
As well as resolution, it’s worth thinking about frame rates. Netflix and Amazon currently deliver 4K video at 24fps. While this looks pretty good, it’s not a patch on the 50fps frame rate used by BT for it’s live 4K service.
Both Netflix and Amazon have hinted that upgrades to higher frame rates won’t be a big deal, so it’s only a matter of time before BT is matched in this regard.
If you can afford both a 4K TV set and superfast broadband service, plus Netflix, Amazon and BT subscription fees, we’d say go for it. There’s not a massive supply of Ultra HD content out there now, but what is there looks pretty damn good.
On the other hand, if you’ve not got a huge amount of cash to spare, we’d advise caution. If content makers decide that 50fps isn’t enough for live 4K, then, as we said above, any TV set labelled as being ‘Ultra HD Ready’ might not be as future proof as you’d like.
Read next: Best 4K UHD Blu-ray players you can buy
What is 8K Ultra HD?
When the progress of technology seems to march on unstoppably, it's good to know there's a limit. In terms of high definition 2D TV, it's called 8K Ultra HD.
8K Ultra HD, also known as UHD-2 and Super Hi-Vision, is a 2D television format created by NHK, the Japanese state broadcaster. It is 16 times more detailed than 1080p Full HD, with 33 million pixels compared to 2 million.
It’s designed to be superior to the human visual system, so that no pixels are visible to the eye, and shoots at twice the rate of normal video so that movement is smooth and realistic.
The Super Hi-Vision image is about 8,000 pixels wide (compared to around 2,000 for Full HD), so it's known outside Japan as 8K Ultra HD. NHK has targeted the Tokyo 2020 Olympic Games for the worldwide launch of 8K Ultra HD.
From Full HD to 8K Ultra HD - looking good, sounding even better
The 8K Ultra HD/Super Hi-Vision specification also includes support for three-dimensional 22.2 surround sound, with three vertical layers of front speakers, two layers of surround speakers, and two subwoofers for bass frequencies.
Conventional home cinema systems are 5.1, with three front and two surround speakers, although we're now seeing 7.1 audio with four surround speakers, and simpler three-dimensional speaker options for the home.
Here's how 8K Ultra HD lines up against 4K Ultra HD and Full HD.
8K Ultra HD vs 4K Ultra HD vs Full HD
|8K Ultra HD / Super Hi-Vision / UHD-2||4K Ultra HD / UHD-1||Full HD|
|Resolution (pixels)||7680 wide x 4320 high||3,840 wide x 2,160 high||1920 wide x 1080 high|
|Total pixels||33 million||8 million||2 million|
|Frame rate||120 frames per second||50 or 60 frames per second||50 or 60 frames per second|
|Standard viewing distance||0.75 x screen height||3 x screen height||3 x screen height|
|Standard viewing angle||100°||60°||60°|
What does Recombu think of 8K Ultra HD / Super Hi-Vision?
"It is the best moving video experience I have ever seen," says Recombu Digital editor, Alex Lane. “The sheer level of detail, smoothness, the sharpness and colour are completely lifelike, and on occasions create an almost three-dimensional image.
"Scenes in low light are also incredibly well-rendered, while the surround sound follows motion around the screen and will make you look over your shoulder to see what’s going on."
Click the image below to enlarge.