It’s been a long-held assumption that the human eye is capable of detecting a maximum of 60 pixels per degree (PPD), which is commonly called ‘retinal’ resolution. Any more than that, and you’d be wasting pixels. Now, a recent University of Cambridge and Meta Reality Labs study published in Nature maintains the upper threshold is actually much higher than previously thought.
As the University of Cambridge’s news site explains, the research team measured participants’ ability to detect specific display features across a variety of scenarios: both in color and greyscale, looking at images straight on (aka ‘foveal vision’), through their peripheral vision, and from both close up and farther away.
The team used a novel sliding-display device (seen below) to precisely measure the visual resolution limits of the human eye, which seem to overturn the widely accepted benchmark of 60 PPD commonly considered as ‘retinal resolution’.
I have well above average vision and my partner has slightly below average. I can see the pixels on a 4k screen at a distance my partner cannot make out pixels on 720p. But both of us find 60Hz, the default for monitors, to be choppy. I think we have reached a fairly good level for pixel density but the refresh rate will keep going up to something like 150-200Hz for displays. Adaptive sync with stable parts being 60Hz and moving parts being higher make sense, as do different refresh rates for different colours. I think eink is also going to play a role as it doesn’t flicker except when updating and it looks very similar to paper in terms of detail density.
Just direct a different laser at each rod and cone in my eye
Pretty cool stuff actually
According to the researchers, foveal vision can actually perceive much more than 60 PPD—more like up to 94 PPD for black-and-white patterns, 89 PPD for red-green, and 53 PPD for yellow-violet. Notably, the study had a few outliers in the participant group, with some individuals capable of perceiving as high as 120 PPD—double the upper bound for the previously assumed retinal resolution limit.
