In case anyone is interested - NVIDIA on PPD: http://phrogz.net/tmp/ScreenDens2In.html#find:density,pxW:1920,pxH:720,size:12.3,sizeUnit:in,axis:diag,distance:31

In case anyone is interested - NVIDIA on PPD: http://phrogz.net/tmp/ScreenDens2In.html#find:density,pxW:1920,pxH:720,size:12.3,sizeUnit:in,axis:diag,distance:31,distUnit:in http://phrogz.net/tmp/ScreenDens2In.html#find:density,pxW:19... They claify that while acuity limits for a person with 20/20 vision is 60PPD, the average acuity is more like 20/15, equating to 80PPD. It looks like NVIDIA put the PPD benchmark for an ideal display at ~92PPD, which would push the acuity limits for just about every human user. That seems reasonable to me. As a point of reference, accounting for binocular overlap values (which I had to hunt for), I calculated PPD's for two of the highest pixel-count HMD's out there: StarVR: 18.6 PPD Sensics dSight: 20.2 PPD I don't have the details needed to calculate Avagent or Hololens PPD's, but I'd venture to say their at this point or lower. So, as you can see, we still have a long way to go. One more note - Displays don't need a constant PPD accros the entire rendered image, thanks to steep visual acuity drop-off relative to FOV angle (1). So, to the OP's credit, perhaps there is still some work that is needed on the PPD metric to account for HMD's that use foveated imaging (2), such that all displays (foveated & non-foveated) can still be compared side-by-side. 1. https://upload.wikimedia.org/wikipedia/commons/thumb/2/27/AcuityHumanEye.svg/500px-AcuityHumanEye.svg.png https://upload.wikimedia.org/wikipedia/commons/thumb/2/27/Ac... 2. https://en.wikipedia.org/wiki/Foveated_imaging https://en.wikipedia.org/wiki/Foveated_imaging