Definition: 4K refers to one of two high definition resolutions: 3840 x 2160 pixels or 4096 x 2160 pixels. 4K is four times the pixel resolution, or twice the line resolution (2160p), of 1080p (1920 x 1080 pixels) that is one of main current consumer high definition resolution standards. The other high definition resolutions currently is use are 720p and 1080i. 4K is now officially designated for consumer products as Ultra HD or UHD, but is also referred to at times, such as in professional or commercial settings as Ultra High Definition, 4K x 2K, or Quad High Definition.
4K resolution is now being employed in an increasing basis in commercial digital cinema projection using the 4096 x 2160 pixel option, where more and more films are shot or mastered in 4K, or upscaled from 2K (1998 x 1080 for 1.85:1 aspect ratio or 2048 x 858 for 2.35:1 aspect ratio).
Also, 4K, under its two official consumer labels, Ultra HD or UHD, is beginning to be implemented into the home theater environment, using the 3840 x 2160 pixel option, via both a growing number of home theater receivers that have either 4K pass-through and/or 4K video upscaling capability, as well as some 3D and non-3D TVs and 3D video projectors.
What makes 4K (Ultra HD or UHD) significant is that with the use of ever larger TV screen sizes as well as video projectors, 4K provides much more detailed and less pixel visible images than 1080p. 1080p looks great up to about 80-inches, and can still look good in larger screen screen sizes, but 4K can deliver an even better looking image for those larger screen sizes.
Also, 3D TVs and Video Projectors currently in use that employ the Passive Polarized Glasses method of viewing, resolution of the resultant 3D image is cut to 540p (960x540 pixels) for each eye, which is 1/2 1080p resolution. In comparison, the same TV displays a 2D image in 1080p resolution.
However, by employing a 4K resolution panel or screen, 3D images viewed via Passive Polarized Glasses can be displayed with 1080p (1920x1080) resolution for each eye. The additional bonus is that when viewing 2D images on the same TV, the viewer will see a full 4K resolution image.
4K Implementation Issues
It is important to note that as of 2014, there is very little video source material available for the consumer market that is actually in 4K resolution, and none from a Disc or TV transmission. The TV, video projector, or outboard video processor, has to upscale the incoming 3D or 2D signal from those sources to the desired 4K resolution.
It is interesting to note is that Blu-ray Discs do have the physical capability to accommodate 4K resolution content, but additional disc layers would have be added to provide enough space for a full length movie. Also, current Blu-ray disc players would probably not be able to play back native 4K content (which means you would have to buy a new player), but in an interesting twist, there are limited number of Blu-ray Disc players have incorporated built-in 1080p to 4K upscaling capability. In other words, such players can upscale current Blu-ray discs to 4K for display on a 4K TV. However, 4K TVs and video projectors, and, as mentioned above, a growing number of home theater receivers also have this upscaling capability.
As a starting solution to provide native 4K content for 4K Ultra HD TVs and video projectors, Sony is actually bundling an external media server and content with its first generation 4K Ultra HD TV, and RED has come out with it RED RAY 4K media player, which will be supported by a 4K content distribution system.
As far as providing 4K over broadcast, satellite, cable, or even streamed via the internet - the required extra bandwidth that would be required could necessitate big infrastructure costs, and with the cost incurred by broadcasters and other providers for the recent required DTV transition, there is no enthusiasm to do it all over again for 4K.
On the other hand, development is in progress on new video compression techniques that might actually be able to squeeze all that additional data into the current HDTV transmission and streaming infrastructure.The Korean Broadcasting Service actually demonstrated possible 4K broadcast transmission technique, and Netflix demonstrated a possible streaming solution for 4K, at the 2013 CES (and will begin limited 4K streaming in 2014). However, before these, or other solutions can be widely implemented, agreement for a specific standard would have to be settled, including provisions for some form of backwards compatibility with current technology.
For more on the state of 4K implementation, read my companion article: What You Need to See 4K Resolution On A 4K Ultra HD TV.
What 4K Really Means for Consumers
The increasing availability of 4K, under the official moniker Ultra HD, can deliver consumers a greatly improved video display image for larger screen applications, and can greatly reduce the ability for viewers to see any visible pixel structure on the screen, unless you place yourself extremely close to the screen. This means even smoother edges and depth - in fact, when combined with faster screen refresh rates, 4K has the potential to deliver almost as much depth as 3D - without the need for glasses.
The implementation of Ultra HD doesn't make your TV obsolete, you will still be able to use it, and current HDTV infrastructure will not be abandoned anytime soon. As Ultra HD is implemented on a wide basis, it will be in addition to, not in place of, current technology, just as 3D is currently. Of course, just as with the 2009 DTV transition, there may come a date and time certain where 4K may become the default standard, but that means a lot of infrastructure needs to be in place, and there must be standardization throughout the entire production and delivery chain, as well as consumer acceptance.
If you feel that you are ready to make the jump into 4K, check out my running list of available 4K Ultra HD TVs.
Beyond 4K and Ultra HD
Yes, they are already thinking beyond 4K - how about 8K? 8K is 16 times the resolution of 1080p. For more on this development, read my article 8K Resolution, as well as a peak at an 8K TV prototype that was on display at CES 2012.
Video Resolution vs Megapixels
Before you leave this article ready to throw up your hands, when you compare 1080p, 4K, and 8K resolution to the pixel resolution of even modestly priced digital still cameras, 1080p (1920x1080) is only 2.1 megapixels, 4K (3840 x 2160 or 4096 x 2160) is about 8.5 megapixels. Only with 8K (7680 x 4320 pixels - 4320p) do you get into the pixel resolution range of the best professional digital still cameras - 33.2 megapixels. In other words, you are most likely taking photos with much higher resolution than you can see on your TV screen, when it comes to video content.
Of course, all the above being said, you are the one that needs to be satisfied with what you are seeing on your TV screen - resolution is one part, but other factors, such as video processing and upscaling quality, color consistency, black level response, contrast, screen size, and let us not forget how the TV physically looks in your room, are also factors to take into consideration.
Also Known As: 4K x 2K, Ultra HD, UltraHD, UHD, Ultra High Definition, 4K Ultra High Definition, 4K Ultra HD, Quad High Definition, Quad Resolution, Quad Full High Definition, QFHD, UD, 2160p