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What is 4K / Ultra HD?

We explain what exactly the manufacturers mean by 4K and UHD

by Steve Withers Nov 1, 2013


  • Consumer electronics manufacturers do love their acronyms - DVD, BD, SD, HD, LED, LCD, OLED, 3D. In fact it’s enough to make the poor consumer think they’re looking at an optician’s eye test chart. Recently we've seen two more acronyms appear, with the manufacturers promoting their new 4K or UHD displays. But what exactly are they?

    Well starting with 4K, it's a higher definition video format that uses an image with a resolution comprised of roughly four thousand vertical lines, hence the acronym 4K. In actual fact the precise resolution of 4K video based on the Digital Cinema Initiative (DCI) specifications is 4096 x 2160 pixels, which is why it's sometimes referred to as 4K2K. This resolution offers over twice the number of vertical lines compared to standard high definition video and effectively creates an image with more than four times the resolution. To put this in perspective, a standard high definition image has a resolution of 1920 x 1080 and is capable of delivering an image comprised of just over 2 million pixels. However a 4K image, with a resolution of 4096 x 2160, can deliver a picture that's comprised of a whopping 8.8 million pixels.
    A 4K image, with a resolution of 4096 x 2160, can deliver a picture that's comprised of a whopping 8.8 million pixels.
    Whilst 4K is used extensively by the film industry, the television industry has adopted a slightly different version that has been christened Ultra High Definition or UHD. This uses a resolution that is exactly four times that of normal high definition - 3840 x 2160 or 8,294,400 pixels - which is why this resolution has also been called Quad HD in the past. The decision to use the term Ultra HD has been largely agreed upon by the manufacturers and does differentiate the standard being used for domestic TVs from that used in the cinema. However Sony, perhaps reflecting their unique position in the market place, are keen to continue using 4K as they feel it is less confusing for the consumer. They might have a point but hopefully this article has helped clarify the difference.

    Film production is usually done at 24 frames per a second, although there have been a couple of recent features shot at higher frame rates. However when it comes to TV the frame rates are higher, with 50 or 60 frames per a second being used depending on where you live. There is talk of the standard for UHD TV broadcasts being even higher than that, possible 100 or 120 frames per a second, maybe even more. This is too high for HDMI 1.4, which means that the majority of UHD TVs will need to be updated once the standard has been agreed. The new 2.0 version of HDMI can handle UHD up to 60 frames per second but even that will need revising if 100 or 120 is the frame rate that is ultimately agreed upon. At present only Panasonic's WT600 UDTV and Sony's VW500 and VW1100 4K projectors include HDMI 2.0.


    Despite the lack of agreed standards, there have been a number of 4K capable displays released to date, with one of the first being launched by Panasonic Professional way back in July 2010. The TH-152UX1 was a native 4K plasma panel with a diagonal screen size measuring a gigantic 152” and including an equally huge price tag of £500,000. Since then, Sony has released their VPL-VW1000ES native 4K projector, which was exclusively demonstrated to AVForums members in late November 2011 and retailed for about £18,000. In late 2013 Sony released their VPL-VW500ES 4K projector, which at just £8,500 smashes the price barrier for 4K projection and makes the Japanese company the only manufacturer to currently offer native 4K projectors. It's also worth noting that the VW500, VW1000 and Sony's new VPL-VW1100ES are the only displays capable of handling both the 4K (4096 x 2160) and UHD (3840 x 2160) resolutions.

    In late 2012 both LG and Sony launched 84" UHD TVs but the £24,000 price tags proved prohibitive to mass market acceptance of the new standard. However a wave of UHD TVs arrived in the middle of 2013, causing a minor price war between the manufacturers. Already there are UHD TVs in screen sizes ranging from 55 to 65 inches and prices that start as low as £2,900. Sony launched their X9005 UHD TV in the summer, closely followed Samsung's F9000 and LG's LA970. Soon we'll see Panasonic's WT600 hit our stores, followed by UHD TVs from Philips, Toshiba and even Finlux. So whether you call it UHD or 4K one thing's for sure, the higher resolution is here to stay and prices are falling fast.
    Ultra High Definition (UHD) is the agreed standard for TV broadcasts and uses a resolution of 3840 x 2160.

    There is currently a sizeable elephant in the room however, which is the general lack of any 4K content. At present the majority of content that will be watched on the new TVs and projectors will be 1080p content scaled up to the full 4K resolution of the panel. This means that the quality of the scaling in these new displays is paramount because whilst you can’t add detail that isn’t there, the video processing needs to take advantage of the additional resolution without adding any obvious scaling artefacts or unnecessary sharpening. This situation isn’t new of course and high definition ready TVs began shipping long before there was ever any high definition content to watch on them, however it does mean that consumers won’t be able to take full advantage of their UHD/4K display’s increased resolution for the foreseeable future.

    The highest resolution source content currently available is 1080p Blu-ray but unfortunately a Blu-ray disc doesn’t have the storage capacity to compress an entire movie at full 4K resolution. There have been Blu-ray players released that can upscale 1080p content to 4K but this is essentially the same processing that is being done in the displays themselves and is nothing more than a stop-gap. In order to encode and deliver an entire movie at a resolution of 4K, a new video delivery system needs to be developed, one with a greater capacity than the current Blu-ray standard. This is certainly in the pipeline, with HEVC codec and 100GB three layer providing a possible solution to true problem of fitting a 4K movie onto a single disc.
    The elephant in the room is the lack of 4K content but a number of solutions are coming.
    Although 4K Blu-ray has yet to be abounded, the good news is that once it has been developed, there will be plenty of content that can be delivered on the new format. This is because filmmakers have been shooting movies on 35mm film for over eighty years and whilst film doesn’t have the physical line structure of video, its effective resolution is at least equivalent to 4K. In addition, a lot of the restoration work done on older films has been archived at a resolution of 4K and new masters are often created at this resolution. Digital filmmaking has also moved to shooting at a resolution of 4K, as have some TV broadcasters, so there should be plenty of content for the studios to release on whatever disc format is announced.


    In terms of other possible forms of 4K delivery Sony have already announced a download service in the US and Netflix have plans to offer a 4K service as well. Of course the viability of any 4K streaming or download service will very much depend on your broadband speed. However if it is fast enough then there is already 4K content that can be downloaded from sites such as YouTube. The satellite providers are also experimenting with 4K broadcasts and we can expect to see some form of limited service launched in the near future. If you want to create your own 4K content but don’t want to shell out for a professional grade camera like the Red Epic, then luckily JVC have released a 4K domestic video camera. Although if you are planning on shooting in 4K, try and avoid too many close-ups as the higher resolution will show every imperfection.

    Over the coming months we can expect to see more UHD TVs hit the stores and, as production costs fall and competition increases, the prices will tumble. However it is worth remembering that all the UHD TVs released to date are essentially just LCD panels with LED backlighting. That means they still suffer from all the limitations associated with LCD technology - poor blacks, backlight uniformity and motion handling. However, waiting in the wings we have 4K OLED and with the promise of superior picture quality and higher resolution, it might prove to be the television equivalent of the Holy Grail.

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