Ultra-high-definition television (also known as 2160p, UHD-1, Super Hi-Vision, Ultra HD television, UltraHD, UHDTV, or UHD) includes 4K UHD (2160p) and 8K UHD (4320p), which are two digital video formats proposed by NHK Science & Technology Research Laboratories and defined and approved by the International Telecommunication Union (ITU).
The Consumer Electronics Association announced on October 17, 2012, that “Ultra High Definition”, or “Ultra HD”, would be used for displays that have an aspect ratio of 16:9 and at least one digital input capable of carrying and presenting native video at a minimum resolution of 3840×2160 pixels.
Ultra-high-definition television is also known as Ultra HD, UHD, and UHDTV. In Japan, 8K UHDTV is known as Super Hi-Vision since Hi-Vision was the term used in Japan for HDTV.
The Ultra HD term is an umbrella term that was selected by the Consumer Electronics Association after extensive consumer research.
There are also many other terms connected to UHD/4K: High Dynamic Range (HDR), Dolby Vision, Hybrid Log-Gamma (HLG), Ultra HD Premium, High Efficiency Video Coding (HEVC), also known as H.265 and Super Hi-Vision.
- 4K UHDTV (2160p) is 3840 pixels wide by 2160 pixels tall (8.29 megapixels), which is four times as many pixels as 1920×1080 (2.07 megapixels).
- 8K UHDTV (4320p) is 7680 pixels wide by 4320 pixels tall (33.18 megapixels), which is sixteen times as many pixels and four times the spatial resolution of current 1080p HDTV, which brings it closer to the detail level of 15/70 mm IMAX. NHK advocates the 8K UHDTV format with 22.2 surround sound as Super Hi-Vision.
The suffix “p” in 2160p and 4320p stands for progressive scan or non-interlaced.
Colour space dynamic range and frame rate
The human visual system has a limited ability to discern improvements in resolution below a certain size and beyond a certain distance.
At current consumer home viewing distances and TV sizes, increasing resolution to 4K may have little perceptual impact, as consumers would not be close enough (the Lechner distance) to appreciate the differences in pixel count between 4K and HD. UHDTV also allows other image enhancements in dynamic range and color, which can improve the perceived difference between 4KTV and HDTV.
UHDTV allows the future use of the new Rec. 2020 (UHDTV) color space which can reproduce colours that cannot be shown with the current Rec. 709 (HDTV and most current 4KTV) colour space.
When dealing with CIE 1931 colour space coverage, the Rec. 2020 colour space covers 75.8%, whereas the digital cinema reference projector color space covers 53.6%, the Adobe RGB colour space covers 52.1%, and the Rec. 709 color space covers 35.9%.
UHDTV also allows for an increase in dynamic range, meaning brighter highlights but also increased detail in the greyscale. UHDTV also allows for frame rates up to 120 frames per second (fps).
Note that UHDTV potentially allows Rec.2020, higher dynamic range and higher frame rates to be applied to HD services, without necessarily increasing resolution to 4K.
4K resolution, also called 4K, refers to a display device or content having horizontal resolution on the order of 4,000 pixels. Several 4K resolutions exist in the fields of digital television and digital cinematography. In the movie projection industry, Digital Cinema Initiatives (DCI) is the dominant 4K standard. In television and consumer media, 4K UHD or UHD-1 is the dominant 4K standard. By 2015, 4K television market share had increased greatly as prices fell dramatically during 2014 and 2015.
By 2025, more than half of US households are anticipated to have a 4K-capable TV (2160p), which would be much faster than the adoption curve of FullHD (1080p).
The name “4K resolution” refers to a horizontal resolution of approximately 4,000 pixels. The use of width to characterize the overall resolution marks a switch from previous television standards such as 480i and 1080p, which categorize media according to its vertical dimension. Using that same convention, 4K UHD would be named 2160p.
There are two main 4K resolution standards:
- The DCI 4K resolution standard, which has a resolution of 4096 x 2160 pixels (256:135, approximately a 1.9:1 aspect ratio). This standard is widely respected by the film and video production industry. The DCI 4K standard has twice the horizontal and vertical resolution of DCI 2K.
- UHD-1, or ultra-high-definition television (UHDTV), is the 4K standard for television. UHD-1 is also called 2160p since it has twice the horizontal and vertical resolution of 1080p.
It has a resolution of 3840 x 2160 (16:9, or approximately a 1.78:1 aspect ratio). UHD-1 is used in consumer television and other media, e.g. video games.
Many manufacturers may advertise their products as UHD 4K, or simply 4K, when the term 4K is traditionally reserved for the cinematic, DCI resolution. This often causes great confusion among consumers.
YouTube and the television industry have adopted UHD-1 as its 4K standard and UHD-2 for NHK/BBC R&D’s 7680×4320 pixels UHDTV 2 with their basic parameter set is defined by the ITU BT.2020 standard. At present, 4K content from major broadcasters still remains limited.
See: 4K UHD
8K resolution or 8K UHD is the current highest ultra high definition television (UHDTV) resolution in digital television and digital cinematography. 8K refers to the horizontal resolution in the order of 8,000 pixels, forming the total image dimensions of (7680×4320).
8K UHD has two times the horizontal and vertical resolution of the 4K UHD with four times as many pixels overall, or sixteen times as many pixels as Full HD.
High-resolution displays such as 8K allows the user to have each pixel be indistinguishable to the human eye from an acceptable distance to the screen. On an 8K screen sized 52 inches (132 cm), this effect would be achieved in a distance of 50.8 cm (20 inches) from the screen, and on a 92 inch (234 cm) screen at 91.44 cm (3 feet) away. 8K resolution can also be used with the purpose of enhancing lesser resolution videos with a combination of cropping technique and/or with downsampling technique used in video and film editing. Resolutions such as 8K allows filmmakers to shoot in a high resolution with a wide lens or at a further distance in case of potential dangerous subject (such as in wildlife documentaries), by intending to zoom and crop digitally in post-production. In this, a portion of the original image is cropped to match a smaller resolution such as the current industry standard for high-definition televisions (4K, 1080p, and 720p).
8K display resolution is the successor to 4K resolution. Full HD (1080p) is the current mainstream HD standard, with TV manufacturers pushing for 4K to become a new standard by 2017.
The feasibility of a fast transition to this new standard is often questionable in view of the absence of broadcasting resources.
As of 2015, few cameras have the capability to shoot video in 8K, with NHK being one of the only companies to have created a small broadcasting camera with an 8K image sensor.
Sony and Red Digital Cinema Camera Company are among the others to be working on bringing a larger 8K sensor in more of their product range in coming years.
See: 8K UHD
The UHD Alliance was created with the consumer in mind. It provides information on premium UHD devices and content to deliver best-in-class home entertainment. The Alliance is also focused on helping consumers build a seamless, integrated and high-quality UHD ecosystem from end-to-end. Premium UHD devices and content will be clearly marked so consumers can easily identify them in-store.
The UHD Alliance is a global coalition of leading film studios, TV brands, content distributors, post-production and technology companies that aim to create a unified criterion for premium UHD platforms, from devices to content including next generation features like as 4K resolution, High Dynamic Range, Wide Color Gamut, High Frame Rate and Immersive Audio. The group is composed of DIRECTV, Dolby Laboratories, LG Electronics Inc., Netflix, Panasonic Corporation, Samsung Electronics Co., Ltd., Sharp Corporation, Sony Visual Product Inc., Technicolor, The Walt Disney Studios, Twentieth Century Fox, Universal Pictures and Warner Bros. Entertainment.
Provide consumers a new differentiated entertainment experience that delivers a premium expression of creative intent using next generation audio‐visual technologies
Define a next generation premium audio‐visual entertainment experience
Promote broad industry adoption
Promote consumer awareness
Reach consensus on quality criteria & a quality regime, assured by the UHD Alliance, across the ecosystem of premium content, devices and services
Enable new business opportunities in premium UHD leveraging cooperative efforts across the end‐to‐end ecosystem
Specify requirements for the Premium quality of UHD Content, Distribution,
Devices, and other elements of the ecosystem
Define criteria that distinguish premium quality ecosystem components while
preserving creative intent
Provide clear definitions, industry guidelines and best practices on emerging technologies, and collaborate with other standards organizations
Develop testing methodologies and certification programs based on the UHD Alliance specifications
Establish UHD Alliance Logo program on certified products
Ensure UHDA‐branded content is guaranteed optimal presentation on UHDA‐branded devices
Promote UHD Alliance Brand and ecosystem to consumers
Establish consumer facing naming and marketing messaging
Encourage consumers to choose UHDA‐branded products for a truly next‐generation experience
High Dynamic Range (HDR)
HDR uses a panel technology deliver this wider colour range and contrast, and it’s very much about brightness and illumination. To view HDR content, you need to have a TV that is compatible with HDR, it’s as simple as that. Although HDR has been talked about for a few years, there are now a set of standards for it, aiming to ensure that consumers are getting some sort of parity in HDR delivery across different devices.
HDR-capable TVs are marketed as 4K televisions. Many HDR TVs have a backlight system that can output about 1,000 nits peak brightness, whereas standard HDTVs typically only output 100 nits, which is the level that Blu-ray and standard TV content is specified to.
HDR10 is an open standard in the industry, TVs will simply say it supports “HDR” and no HDR10, so the consumer will have to assume it supports HDR10 content.
Most of the HDR-enabled content is in HDR10 format, and most TVs support HDR10. This is likely due to its open nature, which means content creators can use it without paying licensing fees.
Samsung, Sony, Sharp, and Hisense are solidly behind HDR10 and currently have no plans to manufacture TVs that support Dolby Vision.
LG, Vizio, TCL, and Phillips are manufacturing TVs that support both HDR10 and Dolby Vision content. Vizio did ship several TVs that only support Dolby Vision, though has now added HDR10 support via firmware updates. HDR10 support can be added via a software update, Dolby Vision can not–it requires special hardware.
Dolby Vision™ transforms the way you experience movies, TV shows, and games with incredible brightness, contrast, and colour that bring entertainment to life before your eyes.
By fully leveraging the maximum potential of new cinema projection technology and new TVs’ display capabilities, Dolby Vision delivers high-dynamic-range (HDR) and wide-color-gamut content. The result is a refined, lifelike imag that will make you forget you are looking at a screen.
Current consumer video delivery and cinema standards are based on the limitations of old technologies and require altering the original content before it can be reproduced for playback—dramatically reducing the range of colours, brightness, and contrast from that captured by modern cameras.
Dolby Vision changes that, giving creative teams the confidence that images will be reproduced faithfully on TVs, PCs, and mobile devices that feature Dolby Vision.
Dolby Vision is a natural complement to Dolby Atmos®. It gives movie, television, and game creators the tools they need to create experiences that preserve the creative intent and let consumers experience truly immersive content without compromise.
For manufacturers of televisions, game consoles, personal computers, and mobile devices, Dolby Vision unlocks the full capabilities of their hardware and creates a premium experience that can increase use and enjoyment of these products.
See: Dolby Vision
Hybrid Log-Gamma (HLG)
Hybrid Log-Gamma (HLG) is a high dynamic range (HDR) standard that was jointly developed by the BBC and NHK. The HLG standard is royalty-free and was approved as ARIB STD-B67 by the Association of Radio Industries and Businesses (ARIB). HLG is compatible with standard dynamic range (SDR) displays.
The BBC/NHK approach to HDR is to replace the gamma of Rec. 709 (which defines the relationship between the signal input coming into the display and the brightness of the output) with a new Electrical Opto Transfer Function (EOTF) that “splices” a log-curve onto the “high end” of Rec. 709. There’s a white paper with more technical detail on the BBC R&D website.
The BBC points out that the BT.709 gamma works pretty well at low to mid levels of brightness, as seen on traditional CRTs. However, to match the HDR TVs that are starting to be available, better performance at high brightness is needed. The BBC believes that its proposal would support displays up to around 5,000 cd/m² with 10 bit grey scale data (it also has a 12 bit proposal for content creation). (Adam said that 1,000 cd/m² is likely to be a practical maximum brightness for a while for consumer TVs)
There are some huge advantages of the BBC proposal for broadcasters, no metadata is needed, which would be an advantage for live broadcast.