Definition - What does Ultra High Definition (UHD) mean?
Ultra high definition (UHD or 4K/8K) is a display resolution standard of at least 3840 by 2160 pixels (8.3 megapixels; 4K), which is double that of Full HD's 1920 by 1080 (2 megapixels). 3840 by 2160 is only the floor value, and resolutions being put on various screens range from this size up to 4096 by 3112 for 4K and up to 7680 by 4320 (33.2 megapixels) for 8K. The Consumer Electronics Association (CEA) clarified in October of 2012 that UHD would refer to any display with a 16:9 aspect ratio and a minimum of 3840-by-2160 pixel resolution.
Techopedia explains Ultra High Definition (UHD)
Ultra high definition is an umbrella term used for display in television and portable electronics such as smart phones and tablets, most commonly referred to as 4K resolution and, subsequently, 8K resolution. This was pioneered and proposed by NHK Science and Technology Research Laboratories and approved and then defined by the International Telecommunications Union (ITU).
UHD results in a very crisp and fine image owing to the high pixel count and allows for manufacturers to make bigger TVs without compromising on image quality. Of course, this also requires that the content be in the same resolution for the quality to be retained. But despite its size, UHD, which is commonly used for television as UHDTV with an aspect ratio of 16:9 or 1.78:1, is still lower than the movie projection industry standard of 4096 by 2160 at 19:10 or 1.9:1 aspect ratio. This means that most movie contents released for UHDTVs are still in a letterbox format.
UHD is not really a breakthrough in technology, as it does not actually require new standards for display; it simply bumps up the pixel count and does not do anything on the video processing end. The screens used for UHD are still the same type of screens used for HD resolution, only that they are not cut into smaller pieces that would form the 1080p or 720p resolution TVs but retain their "mother glass" size. Many industry analysts claim that this is the same gimmick as the megapixel designation for digital cameras, as it does nothing for the actual quality of the image.
Drawbacks of UHD as it stands with current technology include the fact that most content is not in 4K/8K resolution and that the large size of the media requires massive amounts of bandwidth to broadcast, so faster processors and faster Internet connection are required to fully run UHD.