Both 4K and HDR can improve the video quality, but in a different way, when you want to buy a new TV, 4K and HDR are the two most popular concepts of TV manufacturers. General consumers are confused about their true meaning, and often make people feel dizzy. Let's put aside the hype of manufacturers' concepts and understand their true meaning.
What is 4K?
4K refers to resolution, expressed in pixels.
For TVs, the 4K standard is 3,840 x 2160 pixels. This means that 4K TVs display 3,840 (approximately 4K) pixels in the horizontal direction and 2,160 vertical pixels in a 1.78: 1 aspect ratio (more commonly known as 16x9). The total number of pixels is 8,294,400 (about 8 million pixels). 4K resolution is 4 times the number of pixels in 1080p. Four 1080p images can be placed in the space of a 4K resolution image.
Regardless of the screen size, 4K (or any other specified TV resolution) remains the same. However, the number of pixels per inch depends on the size of the screen. This means that as the size of the TV screen increases, the pixel size also increases, or the distance is farther apart to maintain the same resolution.
What you need to pay attention to when buying 4K TV
Although 4K TVs display four times as many pixels as 1080p, this difference may not be noticeable on screen sizes smaller than 55 inches.
In addition to TV sets, the 4K logo is also used in many home theater players, streaming media, ultra-high-definition Blu-ray players and Blu-ray disc players with 4K upgrades. It can also be used in some projectors.
Although 4K TVs can display lower resolution images, to get the best viewing results, you need to connect a compatible 4K device and combine with the production and supply of 4K discs or streaming media content to present the best results.
Except for some Blu-ray discs, or downloading 4K content on the Internet, there are few TV channels that directly support 4K. It can be said that there is basically no.
Most 4K TVs are smart TVs.
The purchase is to check whether your 4K TV supports HDR
If you purchase a high-end package, please check the UltraHD Premium logo.
What is HDR?
HDR stands for High Dynamic Range, which is different from resolution.
In video, dynamic range represents the "distance" (contrast) between white and black in an image. In most cases, this distance is quite narrow, called SDR (Standard Dynamic Range).
HDR is an extension of the distance (contrast) between white and black, in which bright whites can be captured and / or corrected so that they are more intense but do not overwhelm the rest of the image usually caused by overexposure. Dark areas can also be deeper, and no image suffers from underexposure.
When shooting or capturing high dynamic range images, this information is used in post-production to obtain the largest possible white to black range.
The image is also divided to produce more saturated and accurate colors, smoother light and color shadows, and to show more detail in all parts of the image, including dark areas that are usually not visible. The score can be applied to each frame or scene, or as a static reference point for the entire movie or program.
Once HDR encoding is complete, the content can be placed on storage and / or transmission formats (physical, streaming, or broadcast) and viewed on compatible TVs.
How HDR is presented on the TV screen
When a TV that supports HDR detects encoded content, it should appear bright white without smudging or fading, and the dark black display is more pure, showing hidden details.
For example, in a sunset scene, you should see the bright rays of the sun, and also have similar sharpness in the darker parts of the image.
There are two ways for TV to display HDR:
HDR encoded content: The main HDR formats used are HDR10 / 10 +, Dolby Vision, HLG and Technicolor HDR. Content can be encoded in one or more formats. The brand / model of the TV that supports HDR determines its compatible format. If the TV cannot detect a compatible HDR format, it will display an image without HDR enhancement. SDR to HDR processing: Similar to the high-resolution display of low-resolution video signals of a TV to match the display resolution of the TV, SDR video can analyze the contrast and brightness information of the SDR signal and increase the contrast range on a TV with HDR function. Approximate quality of HDR.
Not all TVs with HDR can improve SDR
A TV that supports HDR can display the effect of HDR depending on the maximum brightness of the TV. This is called peak brightness and is measured in Nits.
For example, content encoded in Dolby Vision HDR format can provide a range of 4,000 Nits between the darkest white and the whitest white. Few HDR TVs can achieve such brightness, and there are more and more HDR TVs that can support 1000Nits. But most HDR TVs can't reach this. OLED HDR TVs can be up to 750-800, and many low-end LED / LCD HDR TVs may be as low as 500Nits. However, OLED TVs can display absolutely black, but LED / LCD TVs cannot.
When the TV detects an HDR signal but cannot emit enough brightness to display its full range, it will use tone mapping to best match the dynamic range of the HDR content with the TV's own brightness output capability.
What you need to pay attention to when buying an HDR TV
HDR refers to the extended brightness and contrast range displayed on the TV screen.
HDR has nothing to do with resolution. This means that the application of HDR will not change the basic video resolution. HDR is implemented on top of 4K, not to replace it.
Because of its effect on brightness and contrast, HDR also enhances color. The visual difference between SDR and HDR can be seen on any screen size. However, due to different brightness output capabilities, HDR effects may look different between different TVs.
Not all HDR TVs have SDR to HDR processing capabilities.
When buying a TV with HDR capability, please consider a TV compatible with HDR10 / 10 +, Dolby Vision and HLG formats, and the peak brightness of the TV.
4K and HDR-summary
Whether you are buying a standard 4K TV or a 4K TV with HDR, remember the following points.
Pixels are the foundation for building 4K resolution, and HDR is a way to make pixels look best.
HDR can give 4K greater visual impact.
Since 4K TVs are currently the mainstream sales product, content creators and distributors and TV manufacturers have prioritized HDR on 4K UHD TVs compared to 1080p or 720p TVs.
All HDR TVs are 4K TVs, but not all 4K TVs are HDR TVs.
For best viewing results, please consider TVs that include both 4K and HDR