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4K vs. UHD
The simplest way of defining the difference between 4K and UHD is this: 4K is a professional production and cinema standard, while UHD is a consumer display and broadcast standard. To discover how they became so conflated, lets look at the history of the two terms.
The term 4K originally derives from the Digital Cinema Initiatives (DCI), a consortium of motion picture studios that standardized a spec for the production and digital projection of 4K content. In this case, 4K is 4096×2160, and is exactly twice the previous standard for digital editing and projection (2K 2048×1080). As you can see, 4K clearly refers to the fact that the vertical resolution (4096) is just over four thousand. The 4K standard is not just a resolution, either: It also defines how 4K content is encoded. A DCI 4K stream is compressed using JPEG2000, can have a bitrate of up to 250 megabits per second (Mbps), and 12-bit 4:4:4 color depth and image quality. (See: How digital technology is reinventing cinema.)
Ultra High Definition, or UHD for short, is the next step up from Full HD the official name (that no one uses) for the display resolution of 1920×1080. UHD doubles that resolution to 3840×2160. It does not take a genius to see that 3840 is actually quite far away from four thousand. Almost every TV or monitor that you see advertised as 4K is actually UHD. There are some panels out there that are 4096×2160 (aspect ratio 1.9:1), but the vast majority are 3840×2160 (1.78:1). If you displayed 4K content on one of these 4K displays you would get letterboxing (black bars) down the left and right side of the screen. There isnt yet a specification for how UHD content is encoded (which is one of the reasons theres almost no UHD content in existence), but its unlikely to be the same quality as DCI 4K.
http://www.extremetech.com/extreme/1...the-same-thing
