4K

4K refers to display resolutions with approximately 4000 horizontal pixels. In consumer electronics, 4K Ultra HD (UHD) commonly means 3840 × 2160, a 16:9 aspect ratio and about 8.3 megapixels, four times the number of pixels of 1080p. In professional cinema, 4K may refer to DCI 4K, which uses 4096 × 2160 with a slightly wider aspect ratio.

Standards and color: UHD signal processing uses various color spaces. Rec. 709 is the standard for current HD content, while Rec. 2020 covers wider color gamuts used in HDR. High dynamic range formats associated with 4K include HDR10, Dolby Vision, and HLG, which add brightness levels and richer color through metadata and display capabilities.

Encoding and delivery: 4K content is commonly encoded with codecs such as HEVC (H.265) or AV1. It is distributed via streaming services, Ultra HD Blu-ray discs, and digital cinema. Displays often upscale lower-resolution sources to 4K, and connections typically use HDMI. HDMI 2.0 enables 4K at 60 Hz with common chroma subsampling; HDMI 2.1 expands bandwidth for higher frame rates and features.

History and usage: 4K gained prominence in the early 2010s as televisions and streaming libraries expanded. Ultra HD Blu-ray arrived in 2016. In cinema, DCI 4K has been used for digital projection and distribution since the 2010s, while some cinema projects and cameras continue to use 4K imaging.

Notes: 4K is partly a marketing term and a technical term with multiple variants (3840 × 2160 for UHD, 4096 × 2160 for DCI). Content availability and display capabilities influence the perceived benefit, which depends on source material and viewing conditions. See also: 8K resolution.