What is 4K Resolution? Is 8K 2x Better?
Our lives revolve around screens: monitors for work, projectors for meetings, TVs when we come home from work, and of course, our smartphones. The screen is arguably the most vital part of these devices. In recent years, these displays have been labelled "4K" or "8K." Have you ever wondered what that means? How do these labels affect your viewing experience? By understanding these signs, you will be able to purchase a display device that is best suited to your needs.
In case you don't have time to read the entire article, here's our summary as well:
- Resolution represents the number of pixels.
- 4K resolution is 3840×2160 pixels on a screen most of the time.
- Most TV sets today come with 4K resolutions. Some high-end monitors and projectors are also available in 4K.
- A higher resolution does not guarantee greater clarity. It depends on the pixel density and the distance used. So, no, 8K is not necessarily 2x better than 4K.
- Demand for 4K contents has yet to really take off, and 8K contents will take time to catch on.
"4K" and "8K" are some abbreviations for screen resolution. The screen of a display device is actually made up of extremely tiny pixels. If we drop water on the screen of a mobile phone, we can see many colourful dots inside. They are pixels. The resolution refers to the number of pixels on the screen. The more pixels per unit length, the higher the resolution.
The image above shows a microscope shot of a mobile phone screen. The dots in the image are pixels and they are too small and densely packed to be seen by the naked eye. However, pixels do not have a fixed size. They can be huge and visible to the naked eye -- for instance, pixels on a bus stop screen that look like tiny light bulbs.
Letters and numbers are easily readable on these screens, but the quality is not exceptional. As a result, it is not surprising that the number of pixels on the bus stop screen should be much lower than those on the phone screen.
When it comes to resolution, we typically refer to two aspects: image resolution and screen resolution.
Image resolution refers to the number of pixels contained per unit length. We took a photo with an iPhone and examined the following parameters:
The image above shows a resolution of 3024×4032, which means it has 3,024 pixels horizontally and 4,032 vertically. 3024 times 4032 equals 12192768, which is what we often call a "12-megapixel camera".
Likewise, video is not an exception. When we watch videos on YouTube, we can choose the quality of the video, which is 720P, 1080P, and also 4K.
The P here refers to ‘Progressive’ in ‘progressive scanning.’ progressive scanning is an idea that comes with television. Instead of showing all the pixels in a picture simultaneously, television illuminates a screen by displaying lines sequentially from top to bottom. The reason progressive scanning ever became a feature is because earlier analogue TVs only display the odd lines first, then the even lines are displayed an instant later for a complete image, which we called ‘interlaced scanning’. Progressive scanning produces flicker-free and smoother videos comparing to the interlaced scanning, and modern TVs support progressive scanning because the improvement is absolutely noticeable.
An example would be 1080P, which means the TV needs to scan 1080 lines to display the proper image. This means that there should be 1080 pixels vertically. If you don't understand how it works, you can go to Microsoft Excel, create a table with 1080 rows, and countdown to see if there are 1080 rows exactly.
Ergonomics claims that the field of vision that human eyes can perceive is a rectangle with a length ratio of about 16:9. Therefore, many movies, TV shows, and display devices will produce content and design products according to this golden ratio, which is best suited to the human eye. In that case, how many columns should there be for 1080 rows, in a ratio of 16:9? If you are good with numbers, then you might immediately think of 1920 columns. In other words, 1080P represents a 1920×1080 resolution or 1080P Full HD.
Screen resolution is the number of pixels on a screen. Similar to the definition of image resolution, a 1080P Full HD screen is a screen with 1,920 pixels horizontally and 1,080 pixels vertically. 1080P is still the mainstream resolution for office monitors, but when you purchase a TV, almost all of them are in 4K or even 8K. But what does that mean? What is 4K resolution? We have sorted out the common resolution types for your reference:
The current mainstream TV resolution is 4K resolution size or 3840×2160 resolution, often referred to as UHD or 2160P. For those of you who are sensitive to numbers, 3840 is twice the size of 1920, and 2160 is twice the size of 1080. That means 4K resolution is twice as many pixels as 1080P, both horizontally and vertically. Does that mean 4K video is four times sharper and four times better than 1080P?
And if you think about it mathematically, in terms of area, it might make sense. But as we mentioned earlier, the pixel size is not fixed, and the display area varies from device to device. Even when we use these devices, the distance from our eyes to the device is totally different. Resolution is not the only factor to consider when discussing clarity.
The picture above shows a 55-inch 4K TV and a 6.5-inch 4K smartphone. They both have 4K screen resolution, so who will possess higher clarity? As a first step in answering this question, let's examine how screen size is defined.
Screen size is generally determined by the diagonal length of the screen, in inches. A 55-inch TV is obviously much bigger than a phone, but the resolution is 4K, which means individual pixels are bigger and more visible to the naked eye, and the picture is certainly not as detailed. You can take a closer look at the screen of your phone and then at the screen of your TV if you are able to. Pixels on a TV can be seen with the naked eye, but on a mobile phone, they are hard to see.
This is actually explained by the concept of Pixels Per Inch (PPI), which is typically used to refer to pixel density of a screen. The higher the PPI, the harder it is to distinguish individual pixels with the naked eye, hence greater details in the display.
Thanks to technological advancements, the picture quality of the smartphone screen is so fine that the pixels are almost invisible to the naked eye. Nevertheless, long before the advent of the iPhone 4, smartphone screens generally had low pixel density, so the graininess was still noticeable. The iPhone 4's Retina Display, on the other hand, pushes the pixel density up to 326, which is higher than 300 PPI, the highest pixel density that the human eye can detect. The smoothness of a smartphone screen is no longer a concerning issue.
（Left: iPhone 3GS; Right: iPhone 4）
However, following this logic, the pixel density of the TV is very low. Does that mean 4K TVs aren't sharp enough? No, of course not. We don't watch TV up close as we do with our phones, we watch it at a distance. By viewing it from a certain distance, all the pixel points won't be clearly visible, so the definition will not necessarily be worse than a mobile phone.
Some may still wonder: Do we have to buy a smaller TV to get higher definition? Is it the only way to enhance our watching experience? Let's not forget that pixel density is related not only to the display area but also to the total number of pixels. If you want to maintain a sufficient pixel density without reducing the area, you can just increase the total number of pixels. As 4K is not sufficient for us, we use 8K resolution on the TV, so the display area can be retained and the pixel density can be increased.
There are already plenty of next-gen TVs with 8K resolutions on the market. Nevertheless, to fully experience 8K ultra-high-resolution, you need more than just a TV. Ensure that your input source, cable, and streaming content all support 8K. It’s not that hard to find 8K compatible cables on the market, All you need is a well-made HDMI 2.1 cable. But is there anything to stream in 8K?
The specification of 8K content is way too high. So, it has brought significant challenges to home broadband, as well as film and television production. As a result, streaming media giants like Netflix and Amazon Prime are still focusing on 4K content. None of them have plans to promote 8K content anytime soon. So, it will probably take some time for 8K to truly become popular. However, with enough bandwidth, powerful computer and the right display, you can now stream 8K videos on YouTube, which are mostly landscape footage like Vistas of Norway. You may not find them 4x greater than 4K contents, but it is a sneak peek to the future.