[For more information about viewing distances for 4K and 1080p TVs see "Got A Black Friday 4K TV? Here's What You Need To See All That 4K Goodness"]
4K video seen on a 4K UHD TV is rich with detail that is impossible to reproduce on a standard 1080p HD TV. 4K looks terrific – if you can see it. One thing the TV salesperson may not tell you, is that much, and possibly all, of the additional detail in a 4K image may not be visible if you’re sitting too far from the screen. Here’s what you need to know in order to get the most viewing pleasure from a 4K TV.
Why the detail in a 4K image may not be visible
Imagine yourself standing on a freshly mowed lawn. If you look down at your feet, you can distinguish one blade of grass from the next well enough to count them. If you look at the lawn across the street, you can see that it’s covered with grass, but you can’t count the individual blades.
Your eyes are sharp enough to distinguish one blade of grass from the next at the distance between your eyes and your feet but not at the distance from your eyes to your neighbor’s lawn. The resolving power of the human eye is such that the distance between one blade of grass and the next is too small to be visible at across-the-street distances.
Now think of your TV as being like a lawn where the pixels on the screen are like individual blades of grass. There are more than three times as many pixels on a 4K screen (3840 x 2160 resolution) than there are on a 1080p screen (1920 x 1080). The extra detail in a 4K image is possible because of all those extra pixels. However, if you’re too far away from the screen, you won’t be able to see that detail just like you can’t see the individual blades of grass in the lawn across the street. The human eye can’t resolve the detail in a 4K image if the viewer is too far away.
The factors that limit the resolving power of the eye are the wavelength of light and the diameter of the pupil. You can’t do anything about either of those, they are what they are. However, the science behind what we know about the resolving power of the human eye can be used to calculate the optimal distance between your eyes and the screen so you can see all the detail that’s present in a 4K picture.
How far should you sit from a 4K screen?
If sitting too far from the screen is what prevents you from seeing all the detail in a 4K image, you can solve the problem by moving closer. How close to the screen should your eyes be?
If you sit too close, you’ll be able to see the individual pixels on the screen and the picture will look bad. If you sit too far away, you’ll lose detail as you exceed the resolving power of the human eye. There’s a sweet spot where you can’t see the individual pixels, but you can resolve all of the detail that’s in the picture. Where’s the sweet spot for a 4K TV? It depends on the size of the screen.
The above graph from Rtings.com shows the sweet spot for a range of screen sizes and resolutions. The solid lines are the sweet spots for different resolutions. The color-coded shaded areas above the lines show the distances from the screen where you won't see all the detail in an image, but you will see more than you would with a lower-resolution screen. (A table with optimal viewing distances for 4K and 1080P screens can be found here.)
The information of interest for 4K screens is shown in blue. If you move further away from the optimal viewing distance for a 4K screen (move upward in the graph from the solid blue line), you will eventually hit the optimal viewing distance for a 1080p screen (the solid purple line). If you are sitting at the optimal 1080p distance or further from the screen, your eyes will not be able to resolve the additional detail that is present in a 4K picture. At these distances you might as well be viewing a 1080p screen. In other words, if you have a 4K TV, your distance from the screen should fall within the blue area on the graph.
There are two ways you can use the graph to get the most out of a 4K TV. If your viewing room is arranged so it’s difficult to move closer to the screen, find the distance between your eyes and the screen on the vertical axis of the graph, and read across until you move into the blue area. The screen size shown on the horizontal axis at the point where you hit blue is the smallest screen that will give you at least some benefit from viewing in 4K. Larger screens will let you see more detail.
If you already have a 4K TV, find its screen size on the horizontal axis and read up until you hit the blue area. The solid blue line is your optimal viewing distance, and all the distances shown in blue that lie above the blue line will give you some benefit from viewing in 4K.
A caveat
The distance-from-the-screen numbers you get from graphs like the one shown above or from distance calculators you can find on the internet are close approximations not absolutes. One reason for this is that visual acuity differs across people in a variety of ways.
For example, calculations of optimal viewing distance are usually based on the assumption that the viewer has 20/20 vision. However, only about 35% of adults have uncorrected 20/20 vision, and an additional 50% achieve 20/20 vision with corrective lenses. The calculations also assume the pupil in the human eye is 5 mm in diameter, but the pupil narrows in bright light and widens in the dark. Maximum pupil dilation in the dark also varies with age, reaching a peak when a person is in their 20’s and steadily declining thereafter.
Factors like these may make small differences in recommended viewing distances for some individuals. Be prepared to adjust your distances by small amounts if you find it necessary.
Recommendations
If you have a 4K TV or are thinking about buying one, you don’t want to sit so far from the screen that the added detail in a 4K picture can't be seen. Here’s how to make sure that doesn't happen.
- If you’re planning on buying a 4K TV, think about how much flexibility you have in where you’ll put it and where you’ll sit. Work out an optimal arrangement and some alternatives, measure the distances involved, and use the chart to find a screen that puts you in the blue zone.
- If you have a 4K TV, move as close as possible to the optimal viewing distance. If that feels too close for you, back off until you are comfortable but stay in the blue zone. After you get used to the new position, you can try moving closer a little bit at a time.
- If you sit at the recommended optimal distance and can see the pixels on the screen, your vision may be better than average. Back off slowly until the pixels disappear.
If you found this article helpful, here are more articles with useful information about upgrading to a 4K TV.
