Today's 1920 x 1080 resolution Full HD TVs present us with an image of around 2 megapixels, but a new generation of screens are coming that deliver an 8 megapixel image from hi-res cameras.
With new Ultra HD TVs arriving this year from the big TV brands, it could soon become a format for both broadcast TV and Blu-ray.
What is 4K?
Technically speaking, 4K denotes a very specific display resolution of 4096 x 2160. This is the resolution of all 4K recordings, though many people use 4K to refer to any display resolution that has roughly 4000 horizontal pixels.
Ultra HD TVs have a resolution slightly lower than that - 3840 x 2160. That's exactly four times higher than the full HD resolution of 1920 x 1080.
Many current movie cameras already film above 4K resolutions, for example the RED Epic which can film at a 5K resolution of 5120 x 2700 and the Sony F65 8K which films at 8192 x 4320.
How big is an Ultra HD TV?
So far it's been monster Ultra HD TVs all the way, with Sony's 84-inch 84X9005 and LG's 84-inch 84LM960V leading the way alongside the now-a-bit-old Toshiba 55ZL2, a 55-inch TV whose real claim is glasses-free 3D TV (though there's more where that came from, this time from Philips).
Don't forget the Panasonic TH-152UX1W, a 152-inch plasma that was the first television to boast Ultra HD resolution. Expect 2013 to see a flurry of new Ultra HD TVs at almost acceptable prices, though some will remain monster-sized - like the 84-inch Toshiba 84L9300.
Smaller Ultra HD TVs in 2013
Thankfully, they're getting smaller - and slightly more affordable. The first half of 2013 will see the launch of the 58-inch Toshiba 58L9300, 65-inch Toshiba 65L9300, 55-inch Sony KD-55X9000A and 65-inch Sony KD-65X9000A.
Samsung's delectable 55-inch S9 Ultra HD LED TV - rumoured to cost US$37,900 - will follow later, but are we jumping the gun? After all, OLED TVs are just coming through from LG, and CES 2013 was awash with stunning combinations of both Ultra HD and OLED in prototype form - check out these 56-inch Ultra HD OLED TVs from Sony and Panasonic. These TVs are both fruits of a joint R&D effort by the two Japanese corporations, though we've a soft spot for Samsung's luscious Curved OLED screen, too.
Do I need an Ultra HD TV?
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High definition comes in two flavours: 720p (HD ready) and 1080p (Full HD), both of which offer more picture information than the standard definition formats. The more pixels that make up an image, the more detail you see - and the smoother the appearance of curved and diagonal lines. Ultra HD just takes that on to the next level.
A high pixel count also enables images to go larger before they break up, which suits the trend to bigger TVs. Ultra HD is already making big inroads into the world of digital cinema; almost all major Hollywood movies and TV shows are filmed in 4K - or even 5K.
Of course, perceived picture resolution is as much about viewing distance as resolution. What's the real difference between 720p and 1080p? The answer is about two metres. Increase the pixel density and you can sit closer without the pixel grid becoming obvious; a 2160p image - or Ultra HD - enables you to sit 1.6m from the screen.
Some engineers dispute that you can see a difference between 2K and 4K on any screen less than 100-inches; go larger and the subtle nuances that make up a 4K picture certainly become easier to appreciate.
Can I buy an Ultra HD home cinema projector?
Yes. The first genuine Ultra HD consumer product to hit the streets was the Sony VPL-VW1000ES in 2012, a home cinema projector that borrows technologies originally developed for the brand's commercial digital cinema projectors. Indeed, the VPL-VW1000ES conforms to the Digital Cinema Initiative (DCI) specification, which uses a slightly different resolution (4096 x 2160 pixels) than Ultra HD TVs.
Not to be confused with JVC's DLA-X95R, DLA-X75R and DLA-X55R '4K branded' projectors, which actually deliver a Full HD picture but use pixel-shifting panel technology (called e-shift2) to produce a more textured and detailed image, the Sony VPL-VW1000ES has a native UHD 8.8 million pixel SXRD panel, to deliver true Ultra HD resolution.
The Sony VPL-VW1000ES can accept Ultra HD content over HDMI and display it natively, as well as up-convert any incoming source.
What is Super Hi-Vision?
There's another spanner in the works in the shape of Super Hi-Vision, an 8K format created by Japan's national broadcaster NHK. It was trialled extensively at the London 2012 Olympics by the BBC, but doesn't appear to have much chance of becoming a bona fide format just yet. It's certainly one to watch; at double the frame rate of HD (at 120fps) and with a 7680 x 4320 pixel resolution (that's around 32 megapixels), Super Hi-Vision demos have featured stunning 22.2 surround sound, too, thanks to twin subwoofers each the size of a small car.
Technically Super Hi-Vision also comes under the umbrella of the Ultra HD specification, which could store-up problems for future; how will anyone be able to explain the difference? Super-Ultra HD, anyone? Mega HD?
Will Ultra HD ever be broadcast on TV?
Technically it already is; Eutelsat Communications launched the first Ultra HD demo channel in Europe in January 2013, on its EUTELSAT 10A satellite. In the UK, the BBC has plans to film some documentaries with 4K equipment in 2013, though it's actually trialled Super Hi-Vision - or 8K - broadcasting as recently as the London Olympics.
Just as Planet Earth was one of the first programmes to be shown in HD, the BBC's Natural History Unit have been handed the task of filming Survival in Ultra HD.
South Korea currently leads the way in Ultra HD broadcasting; its KBS Kwanak Transmitter uses DVB-T2 architecture (the tech behind Freeview HD in the UK) to send an Ultra HD signal compressed using HEVC encoding.
A six-month trial of the same tech in the US is scheduled for 2013 that will attempt the broadcast of Ultra HD TV signals in the Baltimore area, while at Mobile World Congress 2013 a Spanish telecoms company, Abertis, conducted an experiment to broadcast Ultra HD TV pictures using DVB-T2 and an 84-inch Ultra HD TV.
Meanwhile, the 2014 World Cup Final from Brazil will be shown in Ultra HD to satellite viewers in Japan, though that country may attempt Super Hi-Vision broadcasts as early as 2016 or 2018.
Will Blu-ray support Ultra HD discs?
Probably, yes, thanks to that new compression codec called HEVC, though the Blu-ray Disc Association (BDA) has yet to ratify anything.
The good news is that there is Ultra HD content already available in the vaults of the Hollywood majors. Increasingly movies are mastered at 4K resolution, both for commercial distribution and restoration projects. Hollywood has also begun shooting movies in Ultra HD and beyond.
Peter Jackson's The Hobbit: An Unexpected Journey was shot on RED Epic digital cameras that are capable of 5K resolution, while Sony's 4K-capable F65 camera is commonly used in film and TV, too. Many US TV dramas are already filmed with one of these cameras, including Made In Jersey, Justified, Save Me and Masters of Sex, according to The Hollywood Reporter, as well as ER, Criminal Minds and Justified.
Quite whether studio bosses actually want this level of picture quality in the hands of consumers remains to be seen. Naturally Ultra HD Blu-ray discs would also require a new generation of BD hardware; so-called 4K-ready Blu-ray players including the new Sony S5100 and Samsung BD-F7500 machines - due for launch in spring 2013 - are only able to upscale regular Blu-ray into Ultra HD-quality, and almost certainly won't play the yet-to-be-invented new Ultra HD discs.
How can I get Ultra HD films onto my Ultra HD TV?
In the absence of shiny discs, the first generation of Ultra HD TV owners will have to rely on 'content delivery systems'. Sony will supply with its new 4K TVs a server containing seven native 4K movies - titles TBC - though heavily compressed downloads from Sony (in summer 2013) and others looks to be the next step.
Destined to be the first 4K player to go on sale, the Redray 4K Cinema Player will cost US$1,450 when it launches in spring 2013. Equipped with a 1TB hard disk, this machine can play 4K content stored on an SD card or USB slot, too - such is the file compression on offer - though it's networked and can stream 4K video from a central server, Lovefilm Instant/Netflix-style.
These two innovations aside, the Ultra HD YB market will be mostly about upscaling for some time to come, and the savvy buyer will carefully consider how good a particular Ultra HD TV is at taking a standard or high definition signal and blowing it up onto a big screen. From the demos we've seen of Blu-ray being upscaled to Ultra HD, the big brands seem to have put a lot of work into this; they all look amazing.
When will Ultra HD become standard?
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The floors of CES 2013 were packed with them, but it could be a difficult birth. With arguments and a lack of industry standards on displays, broadcast and playback of Ultra HD material, the introduction of these cutting-edge TVs will prove complex in the extreme.
Introducing an Ultra HD TV isn't like adding LED backlighting to an LCD screen. It's about orchestrating a seismic shift in the broadcast and entertainment infrastructure, not to mention rewriting the consumer electronics handbook.
Currently the only devices to offer Ultra HD play-out are ultra high resolution PC graphics cards, which typically use a quartet of SDI or HDMI outputs to deliver 8MP of video.
There are also myriad disagreements about what exactly Ultra HD displays and equipment should offer in terms of the exact colour standards, frame rate, compression codec and broadcast technology.
In fact, Ultra HD doesn't yet exist - it's a logo-free collection of guidelines that manufacturers should adhere to. Once they're signed, sealed and agreed and a delivery mechanism - 4K Blu-ray, or 4K downloading - along with a tweaked version of HDMI, is all in place, it's possible that existing Ultra HD TVs won't be up to the task. Who'd be an early adopter?
What about Ultra HD for photographers?
The picture's brighter for digital photographers. The PlayStation3 now displays digital still images at 4K resolution over HDMI (how about a PS4K, anyone?), while Panasonic has been busy prepping prototype displays aimed at image-makers. As well as its 4K resolution 20-inch TV, Panasonic recently presented an identically-sized 4K tablet aimed at designers, photographers and architects.
So despite the excitement in the world of TV, a lack of agreement throughout the industry means that the first enthusiasts to benefit from Ultra HD technology could be photographers, and not cinema enthusiasts.
However, manufacturers have already shown that they think the sweet-spot for Ultra HD TV sits between 55 and 65 inches; isn't that the size you'd like your next TV to be? With a couple of games consoles, some Blu-ray players capable of spitting out Ultra HD resolution images, and a BBC UHD trial channel, we're convinced that within a few years most TV buyers won't be able to resist the temptation of making sure their purchase is at least future-proofed to Ultra HD.
And today's future-proofed TV is tomorrow's cut-price commodity... though is that what they said about 3D TV?