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.
A 4K resolution, as defined by Digital Cinema Initiatives, is 4096 x 2160 pixels (256:135, approximately a 1.9:1 aspect ratio). This standard is widely respected by the film industry along with all other DCI standards.
DCI 4K should not be confused with ultra-high-definition television (UHDTV) AKA "UHD-1", which has a resolution of 3840 x 2160 (16:9, or approximately a 1.78:1 aspect ratio). 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.
The use of width to characterize the overall resolution marks a switch from the previous generation, high definition television, which categorized media according to the vertical dimension instead, such as 720p or 1080p. Under the previous convention, a 4K UHDTV would be equivalent to 2160p.
YouTube and the television industry have adopted Ultra HD 1 [UHD-1] as its 4K standard and "UHD-2" for NHK/BBC R&D's 7680x4320 pixels UHDTV 2 with their basic parameter set is defined by the ITU BT.2020 standard.  As of 2014[update], 4K content from major television networks remains limited. On April 11, 2013, Bulb TV created by Canadian serial entrepreneur Evan Kosiner became the first broadcaster to provide a 4K linear channel and VOD content to cable and satellite companies in North America. The channel is licensed by the Canadian Radio-Television and Telecommunications Commission to provide educational content. However, 4K content is becoming more widely available online including on YouTube, Netflix and Amazon. As of 2015[update], some UHDTV models were available to general consumers in the range of US$400.
The first commercially available 4K camera for cinematographic purposes was the Dalsa Origin, released in 2003. YouTube began supporting 4K for video uploads in 2010. Users could view 4K video by selecting "Original" from the quality settings until December 2013, when the 2160p option appeared in the quality menu. In November 2013, YouTube started to use the VP9 video compression standard, saying that it was more suitable for 4K than High Efficiency Video Coding (HEVC); VP9 is being developed by Google, which owns YouTube.
In February 2014, HIGH TV (High 4K) launched the first Ultra HD, 24/7 General Entertainment TV Channel available worldwide. The channel was the first of its kind and featured a unique mix of Entertainment, Lifestyle, Extreme Sport, Movies and everything in Ultra HD Quality, with 200 hours of New Content each year. The High 4K Team already distributes the channel to Pay TV Operators, IPTV, Mobile, Web TV, etc, as well as distributing 4K content worldwide.
Sony is one of the leading studios promoting UHDTV content, as of 2013[update] offering a little over 70 movie and television titles via digital download to a specialized player that stores and decodes the video. The large files (~40GB), distributed through consumer broadband connections, raise concerns about data caps.
In 2014, Netflix began streaming House of Cards, Breaking Bad and "some nature documentaries" at 4K to compatible televisions with an HEVC decoder. Most 4K televisions sold in 2013 did not natively support HEVC, with most major manufacturers announcing support in 2014. Amazon Studios began shooting their full-length original series and new pilots with 4K resolution in 2014.
|Format||Resolution||Display aspect ratio||Pixels|
|Ultra-high-definition television||3840 × 2160||1.78:1 (16:9)||8,294,400|
|Ultra-wide television||5120 × 2160||2.33:1 (21:9)||11,059,200|
|WHXGA||5120 × 3200||1.60:1 (16:10)||16,384,000|
|DCI 4K (native resolution)||4096 × 2160||1.90:1 (256:135)||8,847,360|
|DCI 4K (CinemaScope cropped)||4096 × 1716||2.39:1||7,028,736|
|DCI 4K (flat cropped)||3996 × 2160||1.85:1||8,631,360|
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 FUHD 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.
The Digital Cinema Initiatives consortium established a standard resolution of 4096 pixels × 2160 lines (8.8 megapixels, aspect ratio 256:135) for 4K film projection. This is the native resolution for DCI-compliant 4K digital projectors and monitors; pixels are cropped from the top or sides depending on the aspect ratio of the content being projected. The DCI 4K standard has twice the horizontal and vertical resolution of DCI 2K, with four times as many pixels overall. DCI 4K does not conform to the standard 1080p Full HD aspect ratio (16:9), so it is not a multiple of the 1080p display.
4K digital films may be produced, scanned, or stored in a number of other resolutions depending on what storage aspect ratio is used. In the digital film production chain, a resolution of 4096 × 3112 is often used for acquiring "open gate" or anamorphic input material, a resolution based on the historical resolution of scanned Super 35mm film.
YouTube, since 2010, and Vimeo allow a maximum upload resolution of 4096 × 3072 pixels (12.6 megapixels, aspect ratio 4:3). Vimeo's 4k content is currently limited to mostly nature documentaries and tech coverage.  Recently YouTube opened 4k to all users. 
This is expected to grow as 4k adoption increases. High Efficiency Video Coding should allow the streaming of content with a 4K resolution with a bandwidth of between 20 to 30 Mbps. VP9 is also being developed for 4k streaming. In 2015 YouTube started to offer [8K resolution] Video. The Full Ultra HD (FUHD) or Ultra-high-definition television (also known as 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 main advantage of recording video at the 4K standard is that fine spatial detail is resolved well. This contrasts with 2K resolutions in which fine detail in hair is displayed poorly. If the final video quality is reduced to 2K from a 4K recording more detail is apparent than would have been achieved from a 2K recording. Increased fineness and contrast is then possible with output to DVD and Blu-ray. Some cinematographers choose to record at 4K when using the Super 35 film format to offset any resolution loss which may occur during video processing.
- "The Ultimate Guide to 4K Ultra HD", Ultra HDTV Magazine, retrieved 2013-10-27.
- Denison, Caleb (15 Jan 2014). "Your 1080p TV is old already: Everything you need to know about Ultra HD 4K". Digital Trends. Retrieved 31 May 2014.
- Anthony, Sebastian (2014-01-07). "No, TV makers, 4K and UHD are not the same thing". ExtremeTech. Retrieved 30 May 2014.
- "Leading Television Industry Players Line Up To Support ‘4K Ultra HD’". 2014 Press Releases (Consumer Electronics Association). 11 November 2014. Retrieved 18 December 2014.
- Lowensohn, Josh (9 July 2010). "YouTube now supports 4k-resolution videos". Tech Culture (CNET). Retrieved 18 December 2014.
- Brown, Heather (16 October 2014). "Good Question: When Will We See Broadcasts In 4K?". Local (CBS Minnesota). Retrieved 18 December 2014.
- "Canadian Serial Entrepreneur to Launch First 4,000-pixel Television Signal, Bulb TV". 11 April 2013. Retrieved 12 November 2013.
- "Young media mogul granted TV licence". 12 April 2013. Retrieved 12 November 2013.
- "Canadian Cat B Channel Plans 4K Video Feed". 16 April 2013. Retrieved 12 November 2013.
- "Bulb TV to turn on 4k". 12 April 2013. Retrieved 12 November 2013.
- "Broadcasting Decision CRTC 2012-268". 4 May 2012.
- Luckerson, Victor (12 November 2014). "Amazon Will Stream in Ultra-High Def 4K by January". Tech Companies (Time). Retrieved 18 December 2014.
- Anderson, Jim (17 December 2014). "4K Ultra HD, High Quality: Red". YouTube. Retrieved 18 December 2014..
- Cox, Joe (27 June 2013). "Seiki launches 39in 4K TV for $699". What Hi-Fi (Haymarket). Retrieved 21 January 2014.
- Greenwald, Will (28 June 2013). "Seiki SE39UY04". PC Mag (Ziff Davis). Retrieved 21 January 2014.
- Frost, Jacqueline B (2009). Cinematography for Directors: A Guide for Creative Collaboration. Michael Wiese Productions. p. 199. ISBN 1-61593019-1. Retrieved 21 January 2014.
- Teoh, Vincent (25 December 2013). "YouTube Adds "2160p 4K" Option To Video Quality Settings". HDTVTest. Retrieved 24 May 2014.
- "Youtube puts in new 2160p 4K option for video-settings". Neo win. Retrieved 24 July 2014.
- Truong, Alice (August 6, 2013). "4K is already playing at a theater near you, but you probably didn’t even notice". Digital Trends. Designtechnica. Retrieved 24 May 2014.
- "Sony Unveils New "4k" Digital Cinema Projector" (press release). Projector Central. June 3, 2004. Retrieved 24 May 2014.
- Quick, Darren (May 31, 2012). "Sony releases world's first 4K home theater projector". Gizmag. Retrieved 24 May 2014.
- Denison, Caleb (September 4, 2013). "Sony feeds starving 4K early adopters with over 70 titles of 4K movies and TV shows". Digital Trends. Retrieved 31 May 2014.
- "Breaking Bad is now streaming in 4K on Netflix", Gizmodo.
- Katzmaier, David (8 April 2014). "Netflix begins 4K streams". CNET (CBS Interactive). Retrieved 30 May 2014.
- Kerr, Dara (17 December 2013). "Amazon Studios to begin shooting original series in 4K". CNET (CBS). Retrieved 30 May 2014.
- "Naughty America: 4K porn is coming, trailer released", Pocket lint.
- "Payserve Launches 4k Ultra-HD Site, Sindrive", Business (AVN).
- "Ultra High Definition Television: Threshold of a new age". ITU. 2012-05-24. Retrieved 2012-08-18.
- David S. Cohen (1 August 2013). "4K Ultra-HD TV Faces Bandwidth Challenge to Get Into Homes". variety.com (Variety Media). Retrieved 30 May 2014.
- "Resolution Table". Resolution Table. Pixar. Retrieved 21 January 2014.
- "4K resolution Definition from PC Magazine Encyclopedia". PC Magazine. 1994-12-01. Retrieved 2010-05-28.
- James, Jack (2006). Digital Intermediates for Film and Video. Taylor & Francis. p. 125. ISBN 0240807022. Retrieved 21 January 2014.
- Jukic, Stephanie. "4K & Ultra HD Resolution". 4k. Retrieved 26 November 2014.
YouTube has had a 4K channel running since as early as 2010 and other developments are definitely on the horizon, especially in countries or regions with excellent internet connectivity that goes above the normal speeds available to most people.
- Ramesh Sarukkai (2010-07-09). "What's bigger than 1080p? 4K video comes to YouTube". Archived from the original on 16 July 2011. Retrieved 2011-08-20.
- "Advanced encoding settings". Google. Retrieved 21 January 2014.
- "Videos tagged "4k"". Vimeo, LLC. Retrieved 21 January 2014.
- Ohannessian, Kevin. "Where Can You Get 4K Video?". TomsGuide. Retrieved 26 November 2014.
YouTube and Vimeo already stream 4K content. Most of the videos are of the nature/documentary variety, with some tech media coverage thrown in the mix. However, Google recently announced plans to make a much larger selection of 4K video available on YouTube, using its new compression technology, called VP9. If your computer has a powerful graphics card that supports 4K and HDMI version 1.4 or higher, you can connect your computer to a 4K television via an HDMI cable. You will likely need high bandwidth to stream the video without any issues, though neither YouTube nor Vimeo has specified the minimum data speed needed for 4K streaming. In addition, Asus, Dell and Sharp already have 4K computer monitors (with more coming this year) that can be used with your computer to watch 4K content.
- Anderson, Jim. "4K Ultra HD Test, High Quality BLUE". YouTube. Retrieved 1 April 2015.
- Template:Cite Url=https://m.youtube.com/watch?v=2Cg7NmXTei0
- Ryan Lawler (25 January 2013). "Next-Gen Video Format H.265 Is Approved, Paving The Way For High-Quality Video On Low-Bandwidth Networks". Tech Crunch (AOL). Retrieved 30 May 2014.
- Wootton, Cliff (2005). A Practical Guide to Video and Audio Compression: From Sprockets and Rasters to Macroblocks. Taylor & Francis. p. 47. ISBN 0-24080630-1. Retrieved 21 January 2014.
- Braverman, Barry (2013). Video Shooter: Storytelling with HD Cameras. CRC Press. pp. 4–18. ISBN 1-13605885-0. Retrieved 21 January 2014.
- Sawicki, Mark (2007). Filming the Fantastic: A Guide to Visual Effects Cinematography. CRC Press. p. 114. ISBN 1-13606662-4. Retrieved 21 January 2014.
- "Axiom Alpha".
- "Zynq-based Axiom Alpha open 4K cine camera proto debuts in Vienna hackerspace". 2014-03-20.
- "Axiom Alpha: Die Open-Hardware-Kamera" [Axiom α: the open hardware camera]. Heise (in German). 2014-05-22.
- What is Ultra HDTV?, Ultra HD TV
- "3D TV is Dead, Long Live 4K", Forbes, Jan 10, 2013
- Gurule, Donn, 4k and 8k Production Workflows Become More Mainstream, Light beam
- What is the meaning of UHDTV and its difference to HDTV?, UHDMI
- "Ultra high resolution television (UHDV) prototype", CD Freaks
- "Just Like High-Definition TV, but With Higher Definition]", The New York Times, Jun 3, 2004
- "Japan demonstrates next-gen TV Broadcast", Electronic Engineering Times.
- "Researchers craft HDTV's successor", PC World (magazine)
- Sugawara, Masayuki (2008), Super Hi-Vision — research on a future ultra-HDTV system (PDF) (technical review), CH: EBU
- Ball, Christopher Lee (Oct 2008), "Farewell to the Kingdom of Shadows: A filmmaker's first impression of Super Hi-Vision television", Musings
- "Visual comparison of the different 4K resolutions", 4k TV
- "Why Ultra HD 4K TVs are still stupid", 4k TV
Official sites of NHKEdit
- Super Hi-Vision, JP: NHK.
- Science & Technical Research Laboratories, JP: NHK.
- type = annual report Super Hi-Vision research, JP: NHK STRL, 2009.