4K resolution
The term "2160p" could be applied to any format with a height of 2160 pixels, but it is most commonly used in reference to the 4K UHDTV resolution of 38402160 due to its association with the well-known 720p and 1080p HDTV formats. Although 38402160 is both a 4K resolution and a 2160p resolution, these terms cannot always be used interchangeably since not all 4K resolutions are 2160 pixels tall, and not all 2160p resolutions are ≈4000 pixels wide. However, some companies have begun using the term "4K" to describe devices with support for a 2160p resolution, even if it is not close to 4000 pixels wide. For example, many "4K" dash cams only support a resolution of 28802160 (4∶3); although this is a 2160p resolution, it is not a 4K resolution. Samsung also released a 51202160 (64∶27) TV, but marketed it as a "4K" TV despite its 5K-class resolution.
Digital cinematography
The DCI standard for cinema usually relies on a 1.89:1 aspect ratio, thus defining the maximum container size for 4K as 4096×2160 pixels and for 2K as 2048×1080 pixels. When distributed in the form of a Digital Cinema Package (DCP), content is letterboxed or pillarboxed as appropriate to fit within one of these container formats.
In the early years of digital cinematography, 2K was the most common format for digitally acquired major motion pictures however, as new camera systems gain acceptance, 4K is becoming more prominent. The Arri Alexa captured a 2.8k image. During 2009 at least two major Hollywood films, "Knowing" and "District 9", were shot in 4K on the RED ONE camera, followed by "The Social Network" in 2010. , 4k cameras are now commonplace, with most high-end films being shot at 4k resolution.