What Is 8K? Should You Buy a New TV or Wait?Time: Jan. 17, 2020
Maybe you've had a 4K TV since they first came out. Maybe you upgraded only recently.
Maybe you're still using a 1080p TV.
Whatever your current screen status is, you've probably heard about what's coming after
4K: 8K. It's the next big jump in TV resolution. And like 4K, the transition requires new
8K is a higher resolution than 4K—and that's it. 1080p screens have a resolution of 1,920
by 1,080 pixels. 4K screens double those numbers to 3,840 by 2,160 and quadruple the
number of pixels. 8K doubles the numbers again, to a resolution of 7,680 by 4,320.
That's four times the number of pixels as 4K, which means it's 16 times that of a 1080p TV.
For context, look really closely at your TV. Try to find a single pixel (not the individual red,
green, and blue lights; those are subpixels, which means you're too close). If you're looking
at a 4K screen, imagine four pixels taking up the space of that single pixel.
If you're looking at a 1080p screen, picture a grid of sixteen pixels, four by four, within that
single pixel. That's 8K. It's much sharper than 4K and much, much sharper than 1080p.
What About HDR?
If you've been paying attention to TVs and 4K, you've heard the term HDR—high dynamic
range. You also might be confused by what HDR is and whether it's different from 4K. HDR
can be a complicated concept, but it's important to understand as 8K continues to develop and
useful to know when you're shopping for a 4K TV.
Resolution—1080p, 4K, and 8K—indicates the number of pixels on a screen. HDR and SDR
(standard dynamic range) define what each of those pixels shows. Each pixel is assigned values
that determine the brightness of its red, green, and blue (and sometimes white) subpixels, which
forms that pixel's color and light, or more precisely, its hue and luminance, respectively.
SDR and the standard color gamut are intentionally limited because of the technical restrictions
of CRT TVs, which determined those standards decades ago. Light is assigned a value between
16 and 238 on a scale of 1 to 255, and color is assigned a value within the Rec. 709 color space,
a small fraction of the full spectrum of visible light.
Broadcast standards were defined within those ranges because CRT displays couldn't accurately
get darker, brighter, or more colorful. This meant any signal sent over the air, cable, or satellite,
and most physical and streaming media, was also limited.
HDR and wide color gamuts take advantage of the greater capabilities of LCD and OLED
screens, using the full available range of values in light and color. For light, that means 1 to
255, often with far more in between levels of light between them thanks to higher bit depths.
HDR TVs use a much wider range of values for light and color, with more steps in between,
than SDR TVs do.
Different types of HDR have different capabilities. Going into the differences of each of them
could be its own story. All you need to know about HDR in this context is that 4K determines
how many pixels, and SDR/HDR determines what each pixel does. Virtually all HDR content
is 4K, but not all 4K content is HDR.
That logic extends to 8K as well. 8K content can be HDR, just as 4K content can. It also can
be SDR, with more limited values for each pixel. Of course, most 8K content will probably
be available in HDR, but we have no way of knowing—there's no consumer 8K content
What Else Do You Need for 8K?
Besides an 8K screen, 8K video requires high speed leading into that screen. Four times as
many pixels, each of which might have more information than pixels typically do, means 8K
video takes up a lot of bandwidth. That's a concern whether you're watching 8K content on
an as-yet uninvented 8K optical disc that supports it or streaming it over a 5G internet connection.
The short answer is that 8K requires (at least) HDMI 2.1. HDMI applies to cables and home
theater devices. That ensures your cables and the source devices you use can handle the
bandwidth requirements necessary to carry 8K content.
Here are the numbers that show why. HDMI 2.1 is a relatively new standard intended for
high- quality 4K and 8K content. It features a maximum bandwidth of 48Gbps—three times
that of the HDMI 2.0 standard (18Gbps), which supports up to 4K60 video. The lower a
bandwidth's connection, the lower the resolution and video frame rate you can send over
it, and the more compressed the video has to be, which hurts fine details. HDMI 2.1 can
handle high-quality, uncompressed 8K video at up to 60 frames per second, and it can
carry uncompressed 4K120 video as well.
So yes, that means you'll probably have to buy new cables. Top-of-the-line certified
HDMI Premium High-Speed cables are rated for only up to 18Gbps; to handle 8K's
requirements, you'll need to wait until the HDMI Forum officially certifies some Ultra
High-Speed HDMI cables, or otherwise look for cables that meet the criteria and have
a maximum bandwidth of 48Gbps (Monoprice currently has two 8K HDMI cables out
of its dozens of different versions).
Your source device needs to support 8K video and have HDMI 2.1 compliance as well.
HDMI 2.1 defines everything in the signal path from source to screen, including the
ports on your media streamer, game system, or Blu-ray player. Even if your device
can play 8K video, that won't matter if it can't actually get that video to your TV.
Is Now the Time to Jump to 8K?
Now is not the time—at least, not for the majority of buyers. You can buy 8K TVs right
now. They're just very, very expensive, and you can't watch any native 8K consumer
content on them. They're early-adopter toys for people who can easily drop five digits
on a TV almost purely for bragging rights.
That said, the LG Signature OLED88Z9P is the most impressive TV we've ever tested;
it's 8K with some very strong upconversion for 4K and 1080p video.
If Not Now, When?
Most people can expect to wait at least two years before 8K TVs are a realistic choice.
In 2020 and 2021, we'll probably start to see 8Ks become the new "premium" TV tier,
still a solid jump in price but presented as the top-of-the-line consumer models instead
of cutting-edge technology you have to special-order.
Expect to see midrange 8K TVs, likely in the $1,000-to-$2,000 range, by around 2022.
The technology will have been polished and optimized to make manufacturing 8K TVs
at a large scale to be sold at those prices by then.