Anyone who has bought a TV, or even thought about buying a TV, in the past few years will almost certainly have come across the term 4K resolution, which is one of the major selling points of the best TVs on the market.
Sometimes referred to as Ultra HD, or UHD, 4K started life in around 2005 with a new standard from the Digital Cinema Initiatives organisation but didn't catch on until some years later, in the mid-2010s, due to the expensive nature of the components needed to make a 4K TV or monitor.
For TVs, the generally accepted resolution of 4K is 3840 x 2160 pixels, or exactly four times the pixel count of 1080p, or Full HD. This increased pixel density offers sharper images, more detail, and better clarity, especially as TVs and monitors have grown larger.
4K adheres to a 16:9 aspect ratio, ideal for TVs, monitors, and projectors.
In some cases, 4K Ultra HD is known as 2160p resolution, a naming convention that derives from HDTV and SDTV formats, and uses the number of pixels along the vertical axis, not the horizontal axis. Today, we're focusing on the CEA Ultra HD standard used for consumer 4K TVs.
What exactly 4K is called isn't hugely important – the upshot is that 4K TVs and 4K monitors offer a much larger number of pixels (both in absolute and per inch terms) than 1080p or 720p HD displays. Both from close up and from distance, 4K just looks better than its predecessors and has now become the standard for TVs.
How 4K differs from HD and 8K resolutions
The transition from HD (1080p) to 4K marked a dramatic improvement in picture quality. Full HD, or a resolution of 1920 x 1080 pixels, contains roughly two million pixels, while 4K has over eight million pixels.
This increase in pixel count leads to finer details, allowing the viewer to sit closer to the screen without seeing or noticing individual pixels. In essence, 4K provides a more immersive viewing experience, especially on larger displays where HD images may start to look soft or pixelated.
The prevalence of ultra-high resolution smartphone displays, like those found on the iPhone 16 Pro, may have also lowered our collective tolerance for lower-quality displays, boosting the appeal of 4K.
While 4K is now considered the standard for higher-end TVs and monitors, 8K resolution, or 7680 x 4320 pixels, represents the next leap, with a resolution that’s four times that of 4K, just as 4K is four times 1080p. An 8K TV screen has an astonishing 33 million-plus pixels. Naturally, the best 8K TVs are very expensive.
At this moment in 2024, 8K content is still very scarce, and the human eye struggles to discern much difference between 4K and 8K except on very large screens. For most consumers, 4K offers the optimal balance of resolution and availability, especially considering the rapid growth in 4K content on disc and the best streaming services.
Where is 4K available?
Many streaming services have embraced 4K movies and TV, often showing entire libraries in Ultra HD, or 4K.
Netflix, Amazon Prime Video, Apple TV+, Max, and Disney+ are some of the leaders, with a substantial number of their original series, movies, and documentaries in 4K. To access them, you'll need a (pricier) 4K subscription tier and a reliable high-speed broadband connection, often upwards of 25 Mbps.
For those who want the highest quality 4K content, physical media remains the best. Video on 4K UHD Blu-ray discs is compressed at a significantly lower rate than on streaming services, and they feature uncompressed soundtracks. Often, you can download such content online if you don't have a 4K Blu-ray player.
What else comes with 4K?
4K isn’t just about more pixels; it’s also about better pixels.
Most 4K displays support High Dynamic Range (HDR), which significantly enhances the contrast and brightness levels of a scene. HDR enables much brighter highlights and deeper shadows, for a more lifelike and dynamic image. There are several standards, including HDR10, Dolby Vision, and HDR10+, with Dolby Vision and HDR10+ providing scene-by-scene, and even frame-by-frame dynamic range optimization.
Another major 4K feature is the wider colour gamut, especially the UHDA-P3 colour space. This enhanced colour range allows displays to reproduce a more extensive palette of colours, resulting in more vibrant and accurate images that are free of the colour banding artefacts typically seen in HD and lower-resolution images. The UHDA-P3 standard makes 4K content look as lifelike as possible.
Finally, loads of 4K movies and TV shows are also paired with immersive audio formats like Dolby Atmos and DTS:X, adding a 3D sound experience, where audio seems to come from all directions, including from above.
Combined with 4K visuals, Dolby Atmos helps to deliver a true cinematic experience at home, even without a fancy home cinema.
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