If you've been eyeing a shiny new 8K television, hoping for a crystal-clear picture that will make you feel like you're watching it through a window instead of a screen, you might want to think twice. According to new research from the University of Cambridge and Meta Reality Labs, there's a limit to how much detail the human eye can actually see. For most of us, our current screens already exceed it.

“At a certain viewing distance, it doesn't matter how many pixels you add…because your eye can't really detect it,” the first author of the study, Maliha Ashraf, of Cambridge University's Department of Computer Science and Technology, told The Guardian.

For most of us, sitting roughly 8 feet from a 44-inch television, a 4K or 8K model provides no visible improvement over a lower-resolution Quad HD (QHD) screen.

To determine the so-called “resolution limit” of human vision, Ashraf and her colleagues designed an ingenious experiment using a 27-inch, 4K monitor mounted on a sliding frame. The setup allowed them to move the screen closer to and farther from the study's participants, measuring how well people could distinguish between images made up of very fine lines in shades of gray or color.

Eighteen participants, all with normal or corrected vision, were shown two types of images in random order — one with one-pixel-wide vertical lines in black and white, red and green, or yellow and violet; and one that was simply a flat gray block. They were asked to identify which image contained the lines.

“When the lines become too fine or the screen resolution too high, the pattern looks no different from a plain grey image,” Ashraf explained. “We measured the point where people could just barely tell them apart. That's what we call resolution limit.”

The researchers then used this data to calculate pixels per degree (PPD) — how many pixels fit into one degree of a person's visual field. This is a measure that answers not “how high is this screen's resolution?” but rather “how sharp does it look from where I am sitting?”

For greyscale images viewed head-on, the team found an average resolution of 94PPD. For red and green images, the number dropped slightly to 89 PPD, and for yellow and violet, it was 53 PPD.

“If you have more pixels in your display, it's less efficient, it costs more and it requires more processing power to drive it,” Rafal Mantiuk, also from Cambridge's Department of Computer Science and Technology, explained. “So we wanted to know the point at which it makes no sense to further improve the resolution of the display.”

Their results suggest that for most of us, sitting roughly 2.5 meters or 8 feet from a 44-inch television, a 4K or 8K model provides no visible improvement over a lower-resolution Quad HD (QHD) screen. In fact, even those with exceptional vision likely wouldn't notice a difference unless they were sitting much closer or watching on a massive display.

“If you have more pixels in your display, it's less efficient, it costs more and it requires more processing power to drive it.”

While the findings may surprise shoppers in the electronics aisle they also have implications far beyond home entertainment. The same principles apply to screens on our phones, tablets and virtual-reality headsets, where pixel density affects not only performance but also cost and energy use.

The research team created a bonus for consumers — a free online calculator where you can plug in your room size, viewing distance and TV specs to see whether upgrading would make any real difference.

Next time you shop for a screen, remember — it's not about the biggest or sharpest display, but the best fit for how you see the world.

The study is published in Nature Communications.