4K UHD

Ultra HD4K UHD is a resolution of 3840 pixels × 2160 lines (8.3 megapixels, aspect ratio 16:9) and is one of the two resolutions of ultra high definition television targeted towards consumer television, the other being 8K UHD which is 7680 pixels × 4320 lines (33.2 megapixels). UHD has twice the horizontal and vertical resolution of the 1080p HDTV format, with four times as many pixels overall.

Televisions capable of displaying 4K resolutions are seen by consumer electronics companies as the next trigger for an upgrade cycle due to a lack of consumer interest in 3D television.

Besides resolution, the UHD standard and related technologies (e.g. HDMI 2.0) include other higher specifications such as a wider Rec. 2020 colour palette.

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.

Toshiba Pro Theatre 84L9300There 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. A4K content from major broadcasters remains limited.


 

4K & UHD Explained

Ultra HD 4KThese two terms are often used together ‘4K UHD TV’, the easiest way of explaining the difference between 4K and UHD is:

  • 4K is a professional production and cinema standard, while UHD is a consumer display and broadcast standard.
    4K” is derived from the Digital Cinema Initiatives (DCI), a consortium of motion picture studios that standardised a specification for the production and digital projection of 4K content.
    4K has a resolution of 4,096 x 2,160, and is four times the previous standard for digital editing and projection (2K, or 2,048 x 1,080).
    4K refers to the fact that the horizontal pixel count (4,096) is roughly four thousand.
    The 4K standard is not just a resolution, either: It also defines how 4K content is encoded. A DCI 4K stream is compressed using JPEG2000, can have a bitrate of up to 250Mbps, and employs 12-bit 4:4:4 colour depth.
  • Ultra High Definition, (UHD), is the next generation of  full HD, which uses a resolution of 1,920 x 1,080. UHD quadruples that resolution to 3,840 x 2,160.
    It is not the same as the 4K resolution used for professional production and cinema.  So when you see a TV advertised as 4K, it is actually UHD.
    There are some TVs that are 4,096 x 2,160, which adds up to an aspect ratio of 1.9:1, though the vast majority are 3,840 by 2,160, for a 1.78:1 aspect ratio (UHD not 4K).

 

Ultra HD Premium

UHD PremiumDeveloped through the collaborative efforts of leading film studios, consumer electronics manufacturers, content distributors and technology companies, the Ultra HD Premium specifications reflect collective expertise from across the Ultra HD ecosystem, as well as significant input gleaned from experiential consumer testing.

The UHD Alliance’s ULTRA HD PREMIUM logo is reserved for products and services that comply with performance metrics for resolution, high dynamic range (HDR), peak luminance, black levels and wide colour gamut among others.
The specifications also make recommendations for immersive audio and other features. These advances in resolution, contrast, brightness, colour and audio will enable certified displays and content to replicate the richness of life’s sights and sounds and allow in-home viewers to more fully and accurately experience the content creator’s vision.

“The diverse group of UHD Alliance companies agreed that to realise the full potential of Ultra HD the specifications need to go beyond resolution and address enhancements like HDR, expanded colour and ultimately even immersive audio.

To ensure products bearing the ULTRA HD PREMIUM logo are certified and conform to the organization’s specifications, the UHD Alliance has designated multiple, independent centers around the globe to handle testing. Companies throughout the ecosystem will work directly with these centers to have their products tested and certified.

The UHD Alliance’s ULTRA HD PREMIUM specifications cover multiple display technologies and reference established industry standards and recommended practices from the Consumer Technology Association, the Society of Motion Picture and Television Engineers, the International Telecommunications Union and others.

UHD AllianceDevices

  • Image Resolution: 3840×2160
  • Colour Bit Depth: 10-bit signal
  • Colour Palette (Wide Color Gamut)
  • Signal Input: BT.2020 color representation
  • Display Reproduction: More than 90% of P3 colours
  • High Dynamic Range
  • SMPTE ST2084 EOTF
  • A combination of peak brightness and black level either: •More than 1000 nits peak brightness and less than 0.05 nits black level
    or
  • More than 540 nits peak brightness and less than 0.0005 nits black level

Distribution

  • Image Resolution: 3840×2160
  • Colour Bit Depth: Minimum 10-bit signal
  • Colour: BT.2020 color representation
  • High Dynamic Range: SMPTE ST2084 EOTF

Content Master

  • Image Resolution: 3840×2160
  • Color Bit Depth: Minimum 10-bit signal
  • Colour: BT.2020 color representation
  • High Dynamic Range: SMPTE ST2084 EOTF

The UHD Alliance recommends the following mastering display specifications:

  • Display Reproduction: Minimum 100% of P3 colours
  • Peak Brightness: More than 1000 nits
  • Black Level: Less than 0.03 nits

The UHD Alliance technical specifications prioritise image quality and recommend support for next-generation audio.

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