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.
4K resolution
Though experiencing rapid price drops beginning in 2013 for viewing devices, the home cinema digital video projector market saw little expansion, with only a few manufacturers (only Sony ) offering limited 4K-capable lineups, with native 4K projectors commanding five-figure price tags well into 2015 before finally breaking the US$10,000 barrier. Critics state that at normal direct-view panel size and viewing distances, the extra pixels of 4K are redundant at the ability of normal human vision. Projection home cinemas, on the other hand, employ much larger screen sizes without necessarily increasing viewing distance to scale. JVC has used a technique known as "e-shift" to extrapolate extra pixels from 1080p sources to display 4K on screens through upscaling or from native 4K sources at a much lower price than native 4K projectors. This technology of non-native 4K entered its fourth generation for 2016. JVC used this same technology to provide 8K flight simulation for Boeing that met the limits of 20/25 visual acuity.