Cambridge and Meta researchers conducted a study confirming that "retinal" resolution is far higher than the 60 pixels per degree figure often cited.While you'll usually see only the panel resolution of a headset mentioned on its spec sheet, what really matters is its angular resolution, or how many pixels occupy each degree of your vision, the pixels per degree (PPD). For an extreme example, if two headsets used the exact same panels but one had a field of view twice as wide, it would have half the angular resolution.Since Oculus widely demoed the DK1 over a decade ago, we've seen the angular resolution of affordable headsets advance from 6 PPD, an acuity that would classify a person as legally blind, to now 25 PPD, while higher-end headsets like Apple Vision Pro and Samsung Galaxy XR reach around 35 PPD, and Varjo XR-4 even achieves 51 PPD in the center. But how high can PPD go before hitting diminishing returns?Meta Tiramisu “Hyperrealistic VR” Hands-On: A Stunning Window Into Another WorldWe also went hands-on with Tiramisu, Meta’s prototype that combines beyond-retinal resolution, high brightness, and high contrast.UploadVRDavid HeaneyIn the XR industry, people often say that it's "generally accepted" that 60 PPD is the limit of what the human eye can discern, since in theory, on paper, it offers 20/20 vision. Meta's Butterscotch prototype from a few years ago with 56 PPD was described as "near-retinal", for example. However, there has been significant skepticism of the 60 PPD figure for years.I tried Meta's 90 PPD "beyond retinal" Tiramisu prototype earlier this year, and while the demo wasn't set up to allow dynamically adjusting the resolution, the researchers behind it told me that they have done so in the lab and could clearly see a difference between 60 and 90. But this was only anecdotal.Now, three researchers have conducted a study at the University of Cambridge experimentally confirming this idea that 60 PPD is not the limit of human perception of detail.One is a Cambridge researcher, one is from Meta's Applied Perception Science team, and the third researcher is both.The experiment setup.Their experiment placed a 27-inch 4K monitor on a 1.6-meter motorized sliding rail in front of the participants, who had their heads fixed on a chin rest and were asked to discern specific visual features head-on as the conditions were varied.The participants were presented with two different types of stimuli throughout the experiment: square-wave grating patterns (both with and without color) and text (both white-on-black and black-on-white).Square-wave gratings, the researchers explain in the paper, are used in vision experiments because prior research suggests that "the foundational visual detectors of the human visual system are likely optimised for similar waveforms". The resolution was varied both by moving the display closer or further away (between 1.1m and 2.7m, distance) and by upsampling or downsampling the spatial frequency of the patterns. The researchers also adjusted the viewing angle between 0°, 1°, and 20°.If you're interested in the full details of the experimental methods, you should read the paper in Nature Communications. It's the results that have fascinating implications for VR and AR.The findings of the experiments.The findings of the experiment, according to the researchers, are that the participants could discern grayscale details up to 94 PPD on average, red-green patterns at 89 PPD, and 53 PPD for yellow-violet patterns.One participant in the study was even able to reach 120 PPD, suggesting that for some people the threshold for "retinal" is double the generally accepted figure.It will be a long, long time before shipping headsets reach anywhere near these figures. Meta's Tiramisu prototype hit 90 PPD only over a tiny 33°×33° field of view, and Tiramisu 2 is aiming for 60 PPD over a 90° field of view instead. And while the study demonstrates that there is a difference, in my experience headsets with even 50 PPD can feel incredibly real to the point where I suspect we won't want to trade off other aspects for further resolution any time soon.Still, it's important that a study has been conducted to discover exactly where the limit to what the human eye can truly discern lies, and it reinforces the fact that while smartphones and tablets are plateauing, VR and AR hardware still has decades of runway for meaningful improvements to steadily arrive.