‘4K is 4K is 4K’, as the writer Gertrude Stein once famously wrote. This might be a slight extrapolation, but the phrase stands as a concise summary of how society perceives 4K technology. More and more often, our televisions, Blu-ray players and projectors come packaged with a neat little ‘4K’ or ‘Ultra HD’ sticker, an indication that most of us take to mean that the device in question meets the very latest standards when it comes to visual entertainment.
If only it were so simple. For starters, 4K and Ultra HD are not actually the same thing. 4K DCI, the likes of which you will find in a cinema, refers to a content resolution of 4096 x 2160, whereas Ultra HD is a consumer iteration with a reduced 2160p (3840 x 2160) resolution. While marketing copy generally uses these terms interchangeably, the ‘4K’ television in your home is likely to use the latter format.
So what about Ultra HD Premium?
While the fundamental specs of 4K DCI and Ultra HD is easy enough to grasp, these do not work to help consumers understand and differentiate between the latest high-end consumer displays – particularly when it comes to understanding recent developments like high dynamic range content (HDR).
To shed light on this, the Ultra HD Premium specification has been formalised by a group called the UHD Alliance as a consumer-friendly means of telling which Ultra HD products are HDR-compatible – that is, deliver a more deep and colourful range of colours.
Devices that are certified as UHD Premium will still deliver the same screen resolution as Ultra HD (2160p), but the new standard requires that displays meet the Rec. 2020 specification, meaning they can match at least 90% of the DCI-P3 colour space (used as the standard chart for defining colour information in a video stream). To put this into perspective, the previous standard – Rec. 709 – only reaches 80% of DCI-P3.
Another boost to picture quality comes in the form of the colour depth achievable under the new specification. By using 10-bit depth, televisions can achieve 1,024 different shades of each primary colour, as opposed to the 256 shades that can be matched with 8-bit depth.
One specification, two sets of rules
One of the complications that comes with defining a set standard for modern television screens is that they are based on diverse technologies that display images in vastly different ways. OLED screens will show richer blacks but will be darker overall than an LED LCD television; this means that they need to be set up in a different manner in order to achieve optimum colour performance.
The UHD Premium specification allows for this, setting two high dynamic range (HDR) specifications with greatly differing minimum levels of brightness and maximum black levels. This means that both OLED and LED LCD displays can be certified, giving customers the ability to understand which devices offer high dynamic range performance regardless of the technology employed.
Unlike the jump from full-HD to 4K resolution, Ultra HD Premium doesn’t mean more pixels; it means richer, more vibrant pixels – which delivers a more noticeable shift in image quality than by simply refining the picture resolution.
As it is with any new industry standard, an inevitable format war has already reared its ugly head. In the case of HDR content, it is Dolby Vision that is competing against the UHD Alliance’s preferred HDR10 media profile for supremacy.Unlike HDR10, Dolby Vision supports 12-bit colour, so it can deliver a larger colour space than its rival. While both require a compatible end-to-end system – including content, player and screen – Dolby Vision systems will additionally be able to support HDR10 content.
Currently, manufacturers are split in terms over which horse to back: Sony and Panasonic have both released HDR-capable players that don’t support Dolby Vision, the likes of LG, Philips and TCL have come out and said they’ll work with both, and Vizio will only support Vision. The same also applies to streaming platforms, with Amazon and Sony Ultra HDR10-only, but Netflix is currently looking at adopting both.
For what it’s worth, the UHD Alliance has said that devices that support either format will be considered for UHD Premium accreditation.
A new generation of Blu-ray
While content will inevitably be an issue for early adopters of UHD Premium set-ups, the good news is that a Blu-ray specification for Ultra HD content has been released. As well as handling 2160p resolution, it uses High Efficiency Video Coding (HEVC) to allow it to support the 10-bit colour and Rec. 2020 that UHD Premium demands. This will undoubtedly go a long way towards increasing the availability of UHD Premium content.
Another benefit of this new player specification is that it adds 3D audio support, meaning that UHD Premium content can be paired with the likes of DTS:X, Auro 3D or Dolby Atmos to create a superior home entertainment experience. Samsung and Panasonic were the first manufacturers to go live with UHD Premium-certified players, although Philips looks set to follow suit with its own model and Microsoft has confirmed that its new Xbox One S console will support UHD Blu-ray films.
For those wondering if their Blu-ray collections and Ultra HD televisions will become outdated with the introduction of this new specification, the answer is a mixed one. When it comes to content, both HDR10 and Dolby Vision are backwards-compatible, which means they will be able to handle playback of lower resolution disks. Likewise, if a television that doesn’t include an HEVC codec, HDR content will be downscaled accordingly.
When it comes to displays, you won’t get the optimum image quality from UHD Premium-certified content unless the accompanying hardware is able to deliver content of the same calibre – so if you buy one, you should prepare to invest in a wholesale upgrade of your home entertainment equipment.
HDR does deliver a mark-up in image quality, but simply putting a UHD Premium screen and Ultra HD Blu-ray player into your living room won’t necessarily result in the best possible viewing experience. While all displays should ideally be calibrated properly to ensure maximum performance, this is a particularly important concern for HDR-enabled displays.
Perhaps more importantly, there is evidence that HDR 4K content performs no better in daylight or high artificial lighting than inferior quality content. An ambient luminance of 5 nits has been mooted as a recommended maximum lighting level when watching this type of content – turning a room lamp on would surpass this. For film lovers looking for maximum image quality, this compromise will probably be worth it, but the casual viewer might find this a bit restrictive just for the sake of a better image.
While the UHD Premium marque is a useful demarcation, it isn’t quite the blanket term that its creators would like it to be. While the UHD Alliance is a trade association that can claim a large swathe of the manufacturers, film studios and other interested parties among its members, it is not an entirely neutral body – and the likes of Vizio have come out in fierce opposition to the standard, stating that the requirements of individual Alliance members mean that the specification is ‘too open-ended’.
In an area as complex as 4K video, there is definitely a need for more coherent consumer-facing information to inform buyers’ choices. UHD Premium status is absolutely a useful tool for helping to sort the wheat from the chaff when it comes to choosing a future-proof Ultra HD video set-up – yet it should be taken as a guide rather than an unequivocal seal of approval.