Technology continues to advance at a staggering pace, and image resolution is no exceptions. Televisions are starting to make the leap from 4K to 8K. There is a certain point though that the human eye cannot discern the difference.
Can the human eye see 8K?
For a person with 20/20 vision, the human eye can see an 8K image with clarity and precision when they are unreasonably close to the display to see the whole image. For a 75-inch television, the viewer would have to be less than 2 and a half feet away to discern the difference between two pixels.
I’ve seen screens so small touting 8K displays. 32” computer monitors and 55” televisions. I really have to wonder what the point is. Here is a chart showing how close you have to be to the screen to be able to tell a difference. I’ve used common screen sizes, and sizes where I’ve actually seen 8K displays.
|Screen Size||Resolution (Same for all – it’s 8K)||Pixel Pitch||Distance to tell a difference between two pixels|
|32”||7,680 x 4,320||0.0810 mm||10.96 inches|
|49”||7,680 x 4,320||0.1354 mm||18.33 inches|
|55”||7,680 x 4,320||0.1401 mm||18.96 inches|
|65”||7,680 x 4,320||0.1643 mm||22.24 inches|
|75”||7,680 x 4,320||0.1900 mm||25.72 inches|
|82”||7,680 x 4,320||0.2078 mm||28.12 inches|
Related Content: Is a Samsung Smart TV an Android TV? What’s The Difference?
Here are examples of 8K displays with those screen sizes.
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The distance (4th column) is the maximum distance away from the display a viewer with 20/20 vision can be in order to tell the difference between two pixels.
Formula for determining distance:
Pixel Pitch = Screen Width / Number of pixels across (7,680)
Distance was determined using an Angular Size Calculator here.
Now, how did I come up with these numbers? I have provided the basic formula, but the details deserve more discussion. The majority of the rest of the article explains how, although there is some discussion at the end about how 8K can be used. There’s a bit of math involved, so bear with me.
Can the human eye see 8K?
To answer this question, we must first understand how the eye “sees” the world. The human eye doesn’t see in pixels. Image if everything we looked at up closely was comprised of little dots?
The way we measure how sharply the human eye can see is called visual acuity. Visual Acuity is the clarity or sharpness of vision. In other words, your eye’s ability to recognize small details with precision. (Can you see how this relates to discerning pixels on a screen?)
You are probably familiar with the Snellen chart!
This is the most common way visual acuity is measured. Let’s take a look at the physics of what is going on when you look at an eye chart.
Measuring Visual Acuity
Visual acuity is typically measured in what is called “arc minutes”. If you have recently taken geometry or trig, you might be familiar with this terminology, but I’m willing to bet most of us have long forgotten these details since high school.
Let’s review briefly. A circle is divided up into 360 degrees. 1 degree is divided up into 60 arc minutes.
|Degree||1/360 of a circle|
|Arcminute||1/60 degree, 1/21600 of a circle|
The Snellen chart is designed so that you have to be a specific distance away. That is so the line of letters that represent 20/20 vision take up 5 arc minutes of your vision. If you were closer, the angle would be greater. If you were further, the angle would be smaller.
At that distance, each letter takes up 5 arc minutes (I know I already said that, but the next part is important). The individual limbs of the letters and the spaces are 1 arc minute.
That means if you have 20/20 vision, you are able to differentiate objects with a precision of 1 arc minute.
Visual Acuity and Pixels
Now let’s tie that information back to how we view pixels on a screen. To do this, we first need to look at pixel pitch.
Pixel pitch is the distance between the center points of two pixels. So, if you have two pixels side-by-side that are touching, then this is how you measure the distance. Another way to think of it is the width of a pixel, assuming the pixels are touching side-by-side.
This is the case in most consumer displays. In most types of screens that an average consumer uses, the pixels have no space in between them. Think TVs, computer monitors, smartphones, tablets, etc.
For screens of the same resolution, as the screen gets larger, the pixel will be larger. This means the screen will have a larger pixel pitch, as each pixel becomes wider.
For example, let’s say you have two screens with Full HD resolution (1080 pixels across). One screen is a 65”, and the other screen is a 55”. The screen both have the same number of pixels going across, so that means the 65” will need larger pixels to fill up the larger distance.
Viewing Distance from The Screen
As can be seen in Measuring Visual Acuity section, the further away from an object you are, the more area a given angle covers. That’s why you have to stand a set distance from the Snell eye chart.
The same math applies to viewing a screen as well. You the viewer want to be far enough away that 1 arc minute covers more than 1 pixel. (Remember, that’s the visual acuity of a person with 20/20?)
A lot of TV manufacturers have recommended viewing distance. Samsung’s recommendations can be seen on their website here. A common recommendation is that the viewer is twice the distance away from the TV as the TV is big.
Recommended TV size = Viewing distance (in inches) * 2
Or if we rearrange the formula:
Viewing distance (in inches)/2 = Recommended TV size.
For example, if you have a 60-inch TV (as measured diagonally),
60” * 2 = 120”
The recommended viewing distance is 120”, which equals 10 feet. Depending on who you ask, this can be plus or minus a few feet.
Can you see the difference between 4K and 8K?
Given the above information, we can adequately answer that question.
The optimal distance for a 65” screen is about two feet for 8K and a little over 4 feet for 4K. If you sit closer than 4 feet, you will notice a difference. However, most people don’t sit that close to the TV.
The average person sits about 8 – 12 feet away from their TV, which matches the recommended distances for TV’s in the 55” – 75” range. I’d guess that most people don’t physically have room in their house to sit much further away.
Sitting an average distance of 10 feet away from a TV, a person cannot see the difference between 4K and 8K for a screen size that is 75” (diagonally) or less.
Is 8K Pointless?
Consuming 8K content may be pointless, but recording in 8K is a different story.
8K is pointless for those who intend to view the content, such at watching TV or a movie. However, recording video in 8K is useful for security cameras and also useful for video editors in post-production. 8K is also useful for immersive applications, such as virtual reality.
Recording video in 8K enables video editors to apply editing techniques, such as image stabilization, and maintain a 4K video output. 8K opens up a plethora of editing options. Cropping, zooming in, image stabilization and AI tracking can all be done in post-production.
This doesn’t only apply to entertainment productions either. Think about the applications for security cameras in using 8K video. An 8K video would allow cameras to identify a person from further away, or perhaps for home security cameras to better read license plates.