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The newest 8K TVs have 33 million pixels - but can you even see that many?

Hosted by: Stefan Chin

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[♪ INTRO].

The newest 8K Ultra High-definition TV screens have a mind-blowing 33 million pixels. Those are the tiny individual points of light, each with a certain color and brightness, that add up to make the picture on the screen.

And that's 4x as many pixels as its predecessor, the 4K screen. And more pixels means a sharper, more detailed image. But before you run out and buy the latest upgrade, you might consider whether you can even see the increased resolution.

And… it's very likely that you can't. Now, before we get too far into this, we should note that you'll only get the full benefits of an 8K screen if you're looking at 8K video. Most movies and TV shows weren't recorded in 8K.

But, let's just assume for the moment that 8K video is available for your favorite type of media, and everything else you need to watch it is in place—like, your internet connection is fast enough to deliver 8K streaming. Since the whole point of an 8K screen is the increase in detail, one could argue that the question of whether an upgrade is worth considering ultimately boils down to your eyesight. And there's a limit to how much detail the human eye can resolve.

Beyond the limit of human perception, two dots, or two pixels, will blur together and look like one. The point at which this happens depends on the size of the dots and how far away they are. Once you reach this limit, adding more details won't make the image look any sharper.

And your eye's visual limits are defined by its physical features. When you take in a scene, the lens of your eye focuses a miniature image of whatever you're looking at onto the back of the eyeball, where it's projected across an array of light-detecting cells called photoreceptors. Each one gets a tiny piece of the image.

It responds according to the brightness and color of the light in that piece. So if an image is so small that two pixels fall onto one photoreceptor, you'll see them as one blended light source. To see both as separate, the image needs to be big enough so that the two pixels span at least two photoreceptors.

For example, take those eye charts at the doctor's office. If you walk right up to it, you'll be able to make out the littlest letters with ease. But if you stand at the proper distance of 6 meters, or 20 feet, the image of them inside your eye is a lot smaller.

That means the ink and the space around it have started to fall on the same photoreceptors, so the letters have blurred into illegible smudges. That's why the eye's visual acuity is measured as an angle: the angle created when you draw imaginary lines between your eyeball and two separate points at the farthest distance you can resolve them. If you have 20/20 vision, that angle is one-sixtieth of a degree, or one arc minute.

And using this angle and some math, you can calculate the highest pixel resolution you can see for any distance. Say you have 20/20 vision, and you sit a comfortable 2.5 meters, or about 8 feet, from your TV. From there, you can just about fully enjoy a 1080p HD video on a 60-inch screen.

It has about 37 pixels per centimeter, and your eye can resolve about 28 pixels per centimeter at that distance. So the image will be detailed, but not pixelated, because the pixels are blurring a bit. If you upgrade to 4K or 8K, though, you won't be able to discern the increase in resolution.

You could buy a bigger TV—and sure, as screen resolution has gone up, people around the world have been doing that. But you still have to fit your TV into your living room. And to get roughly the same pixels per centimeter, you'd need a 120-inch 4K screen or a 240-inch 8K screen.

But that 28 pixels per centimeter number is based on 20/20 vision— if your vision is better than that, you might be able to resolve more pixels per centimeter, so you might notice a difference between a 60-inch 1080p and a 4K screen. But unless you have the best possible visual acuity — about 20/8 vision — if your couch is 2.5 meters from a 60-inch TV, you're simply not going to be able to see the additional pixels of an 8K screen. You could move your couch closer, of course.

To see 4K in its full glory, you'd need to sit about 120 centimeters or 4 feet away from that 60-inch screen. And if you upgraded to a 60-inch 8K TV, you'd need to get even closer— a mere 61 centimeters or 2 feet… which makes for a pretty cozy viewing experience. And there's a catch to that, too.

If you get too close, the angle between your eyes and the screen gets so wide that the edges of the image extend out of your visual field— meaning, you can't take in the whole screen at once. A 60-inch TV maxes out your visual field when it's about 1 meter away. But the average person can't perceive the full pixel resolution of an 8K TV of that size until they're less than a meter away from it!

You can see how this starts to become impractical. Now to be fair, human vision is complex, and the newest. TV models may have benefits beyond pixel resolution.

Newer, higher-resolution screens often come with other upgrades, like higher frame rates, more contrast, and a greater color range. These features can help improve picture quality, especially for images that move. So a new TV will probably look better than your old one— even if it's the exact same resolution.

And we'd be remiss if we didn't mention that there are also socioeconomic and psychological aspects to TV ownership— like how much you can actually afford, and whether you think it'll make you look cool to have the latest model. So really, whether an 8K TV is “worth it” to you doesn't just boil down to how well you can see the finer resolution video. Ultimately, the science can't tell you whether or not you should buy that 8K TV.

But, it can tell you whether you can perceive those extra pixels— and, odds are, unless you have the space for a huge TV or sit really close to it, you can't. Thanks to Patrick Gilmore for asking! And thanks to all our patrons who voted for this question in our poll.

If you support us on Patreon at any level, you can submit questions like this and help us decide which ones we actually answer in episodes. There are other things you can get, too, like blooper reels or even your name in the credits! And that's on top of knowing that you're a big part of making SciShow happen - so thanks for doing that.

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