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Q: If you want to create a perfect home theater, TV or projection, sound placement and distance are obviously crucial. At the same time, with the popularity of 4K TVs, many users are also interested in replacing a larger and clearer TV. Then, if viewing distance needs to be adjusted, how can we judge?
A: 1080P is the most popular LCD TV resolution standard at present, which means that the screen has 1920×1080 resolution, progressive scan, and the total number of pixels is 2,073,600. Of course, in the case of the same resolution, the bigger the screen is, the easier it is for you to see the pixels, so there is a certain rule for the optimal placement distance. 
What about 4K TV?
So, if it is the current popular 4K TV? Obviously, the resolution of 4K TVs is higher (such as 38402160 or 40962160), which is at least four times that of 1080P. Does that mean that the distance is four times longer? of course not. Basically, the placement distances of the same-size 4K TVs and 1080P TVs are basically the same. Pixels are not a problem. It may be necessary to rethink the perspective. THX believes that the viewing angle of 1080P TV should not exceed 40 degrees, while 4K TV does not exceed 60 degrees.
Content determines picture quality and viewing effects 
Whether your TV is 4K or 1080P, the final result depends on the quality of the source. For example, traditional broadcast television is generally 480i, 480P, 720P or 1080i (where i stands for interlace scanning, P stands for progressive scan), DVD is 480P, and Blu-ray is 1080P (4K Blu-ray will be available soon). As for streaming media content, dynamic adjustments are made according to the bandwidth, and even if the resolution is fixed, the encoding rate may be different.
Give a simple example. The upper image in the figure above is the original resolution, and the lower image is the original resolution reduced by 4 times, and the original resolution is reset. The effect gap is quite obvious. If you use a 4K TV to play unprocessed 1080P video, the effect is similar to the above image. In this case, you may need to adjust the seat distance appropriately so that it is farther away from the so-called gold, in order to get better results.
TV viewing distance health issues 
My mother told us since she was a child: Do not always watch TV. It is not good for the eyes. So, if you sit too close to the TV, will it affect your health? Previously, due to the use of cathode ray tube imaging (commonly known as picture tubes and CRT TVs), televisions had X-ray radiation and had a certain impact on the human body; after the display was fully liquid crystallized, this problem did not exist.
What about eye fatigue? Dr. Lee Duffner of the American Academy of Ophthalmology said that sitting too close will indeed cause eye fatigue, but usually a good night's sleep will solve the problem. There are also ophthalmologists who say that as long as users watch TV at a distance that does not cause their eyes to be uncomfortable, there is no problem.
Of course, watching TV is not a healthy activity. This is because of sedentary and fixed postures. It also takes longer, obviously not as good as exercise.
Come up to see how far the 4K TV distance is most suitable
The video and video certification company THX has released a formula for the placement distance of high-definition televisions, dividing the TV size by 0.84 (eg 50-inch TV, 50/0.84 = 59.5 inches, approximately 1.5 meters). Of course, not everyone agrees with the THX standard. The speaker manufacturer Aperion Audio recommends that the viewing distance of a 50-inch 1080P TV should not be less than 6.5 feet (about 1.9 meters). In fact, it is not much different from the THX standard. Obviously, there is already a relatively universal standard range for the placement of 1080P TVs.