4K resolution
This resolution is used mainly in digital cinema production, and has a total of 8,847,360 pixels with an aspect ratio 256135 (≈1910). It was standardized as the resolution of the 4K container format defined by Digital Cinema Initiatives in the Digital Cinema System Specification, and is the native resolution of all DCI-compliant 4K digital projectors and monitors. The DCI specification allows several different resolutions for the content inside the container, depending on the desired aspect ratio. The allowed resolutions are defined in SMPTE 428-1: The DCI 4K standard has twice the horizontal and vertical resolution of DCI 2K (), with four times as many pixels overall.
Graphics display resolution
This resolution, sometimes referred to as 4K UHD or 4K2K, has a 16:9 aspect ratio and 8,294,400 pixels. It is double the size of Full HD (19201080) in both dimensions for a total of four times as many pixels, and triple the size of HD (1280720) in both dimensions for a total of nine times as many pixels. 38402160 was chosen as the resolution of the UHDTV1 format defined in SMPTE ST 2036-1, as well as the 4K UHDTV system defined in ITU-R BT.2020 and the UHD-1 broadcast standard from DVB. It is also the minimum resolution requirement for CEA's definition of an "Ultra HD" display. Prior to the publication of these standards, it was sometimes casually referred to as "QFHD" (Quad Full HD).