What Is 4K Resolution? Overview and Perspective of Ultra HD

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). The other high definition resolutions in use are 720p and 1080i.

4K resolution is used in commercial digital cinema using the 4096 x 2160 option, where many films are shot or mastered in 4K by upscaling from 2K (1998 x 1080 for the 1.85:1 aspect ratio or 2048 x 858 for 2.35:1 aspect ratio).

Under its two official consumer labels, Ultra HD and UHD, 4K is well established in home theater, 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 TVs, video projectors, and source devices, such as media streamers, Ultra HD Blu-ray Players, and Blu-ray Disc players that employ 4K upscaling.

In addition to Ultra HD or UHD, 4K is also referred to in professional settings as 4K x 2K, Ultra High Definition, 4K Ultra High Definition, Quad High Definition, Quad Resolution, Quad Full High Definition, QFHD, UD, 2160p

Why 4K?

What makes 4K significant is that with the use of ever larger TV screen sizes as well as video projectors, provides much more detailed and less pixel visible images than 1080p. 1080p looks great up to about 65-inches, and can still look good in larger screen sizes, but 4K can deliver an even better-looking image as screen sizes continue to increase.

How 4K is Implemented

There are plenty of 4K Ultra HD TVs available, as well as a small number of 4K and 4K-enhanced video projectors.

4K content is available from several streaming sources, such as Netflix, Vudu, and Amazon, as well as via the Ultra HD Blu-ray Disc format and players. It is important to note that although there are many Blu-ray disc players that upscale standard 1080p Blu-ray disc to 4K, only an Ultra HD Blu-ray Disc player can play discs that contain a native 4K resolution.

On the cable/satellite part of the equation, DirecTV is able to deliver both pre-recorded and live 4K content via satellite to its subscribers (provided they have both a compatible satellite box and subscribe to the appropriate plan). On the cable side, things are in the works, but nothing substantial yet.

However, over-the-air TV broadcasting is where things are really lagging. 4K TV broadcasting is still being field tested with South Korea taking the lead, followed by the U.S. However, one big obstacle is that the electronic infrastructure needed is not compatible with the current HDTV broadcasting system.

What 4K Really Means for Consumers

The increasing availability of 4K delivers 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. This means even smoother edges and depth. 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 a 720p or 1080p TV obsolete (although, as 4K Ultra HD TV sales pick-up and prices some down, fewer 720p and 1080p TVs are being made), and the current HDTV TV broadcast infrastructure will not be abandoned anytime soon, even as ATSC 3.0 begins to become available for use for content transmission.

Of course, just as with the 2009 DTV transition, there may come a date and time certain where 4K may become the default TV broadcast standard, but that means a lot of infrastructure needs to be in place.

Beyond 4K and Ultra HD

What lies beyond 4K? How about 8K? 8K is 16 times the resolution of 1080p. Several prototype 8K TVs have been displayed in the past several years and there are some 8K monitors in use for professional applications, but affordable options for consumers is still some ways away - probably in the 2020 to 2025 time frame.

Video Resolution vs Megapixels

Here's how to compare 1080p, 4K and 8K resolution to the pixel resolution of even modestly priced digital still cameras:

1080p (1920x1080) is 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. You are most likely taking photos with much higher resolution than you can see on your TV screen when it comes to video content.

Color, Contrast, and More

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 factors such as video processing and upscaling quality, color consistency, black level response, contrast, screen size, and even how the TV physically looks in your room all need to be taken into consideration.

For a more detailed look at how contrast and color are being improved, along with 4K resolution, check out our companion articles: HDR: Dolby Vision, HDR10, HLG - What It Means For TV Viewers and Color Perception and Your TV.