One exciting thing about microLEDs is they can achieve much higher pixels per inch. Before Apple’s big Retina push, PPI was around 80-120. It went to around 200-300 with Retina. Researchers making microLEDs in the lab have gone as high as 6000 PPI, and something in the low thousands seems quite plausible for commercial technology. Apple could conceivably bring in “Double Retina” at 800 PPI, or they could go straight to “Double Double Retina” at 1600 PPI.
It’s often claimed the human eye can’t see above 300 PPI; this is even more misleading than the claim that the human eye can’t see above 30fps (we all know there’s a distinct visual difference between 30fps and 60fps, and most people are able to detect the difference between 60fps and 144fps as well). The PPI limit of the eye depends on how brightly lit the subject is and how far away one is viewing it; for a real upper limit you might use something like the maximums of https://lobsangstudio.com/ls_pixel.cfm which says at 6 inches viewing distance under 10,000 lux (bright sunny day), the eye could go as high as 1200PPI. The fact that microLEDs offer the potential to go beyond even the maximum of generous estimates in best conditions is very exciting, it’s like Formal Proof version of Retina rather than the current Good Enough.
The point of Retina is that the pixels aren't visible at normal viewing distances. You really shouldn't be using any (non-VR) screen 6 inches away. At 18 inches the effective PPI would be 400, so not much more than retina even at insane brightness.
The Retina value is “for a specific visual acuity (usually 20/20), at a specific viewing distance (usually 18 inches), at a specific brightness (usually indoor office lighting), individual pixels cannot be distinguished”. If you have better than 20/20 vision, you need a higher PPI to achieve “Retina” (individual pixels not distinguishable). Chuck Yeager, the fighter pilot guy, famously had 20/10 vision, and it’s estimated up to 1% of the population might have 20/10 vision as well. It is apparently quite common among elite athletes to be 20/15 or better.
Viewing distance also varies a lot - I recall reading somewhere the empirical observed viewing distance for smartphones is between 6 and 15 inches sitting and between 4 and 9 inches lying down. Environmental brightness also varies, obviously.
Just to give a personal example, my near vision was measured at 20/16 with correction, I am currently holding my phone 7 inches from my eyes, and I have my room lit with four 1500-lumen bulbs (to simulate daylight). I don’t know what the correct PPI would be there, but it’s obviously going to be higher than the usual amount.
In addition, it’s not clear that “cannot distinguish individual pixels” is even the same thing as “no more visual quality can be gained with higher pixel density”. At 30fps the human eye can’t distinguish individual frames, but 60fps still has visual benefits over 30fps, and many people are able to consistently detect the difference between 60fps and 144fps. Past 144fps is when you get to “no more visual quality can be obtained by higher frame rates” (as opposed to proxies like “individual frames are not distinguishable”). I suspect a similar thing is true for pixel density.
But as I said originally, I’m excited that microLEDs might make it viable to have screens with a pixel density not just “beyond what’s reasonably good enough in most circumstances”, not even “beyond what’s detectable by most people in all but the best circumstances”, but in fact well into “provably beyond the limits of what the best human eyes can detect in the best possible conditions at impractically close viewing distances”.
> It’s estimated up to 1% of the population might have 20/10 vision as well. It is apparently quite common among elite athletes to be 20/15 or better.
On the standard eye test chart where 20/20 vision is the ability to read the bottom row, I could usually read the copyright fine print below the 1-inch high block letters!
To me it always felt like that is normal vision, and 20/20 is taking an average that includes a bunch of people with poor eyesight. Like... the average person has less than 2 eyes, less than two legs, etc...
The history of 20/20 being considered normal is quite interesting, essentially it comes down to being simply what Herman Snellen defined as normal (on the plus side, he had a few years practice as an ophthalmologist before he invented his chart and it was based on standardizing several other charts in use, so it was based on a lot of experience; on the minus side, it was invented in the 1860s).
It’s been a while since I read up on it but my recollection is that the healthy eye in a young patient (“normal” in the sense of “lacking any deficiencies whatsoever”, not in the sense of “average”) should be around 20/12, with natural variation between 20/10 and 20/16, and 20/20 indicating (extremely minor) deficiencies. The theoretical perfect eye from an optical standpoint, something like if you were to grow an eye from the same materials as a real human eye but you could specify exact dimensions etc., is something like 20/7 (as in, you can’t get better optical resolution than that given the optical properties of our lenses and the distribution and size of our light receptor cells).
Eyes are extremely complicated structures that are either very sensitive to environmental conditions, or that the body is very willing to cut corners on given the slightest provocation, so few people get that “perfect” vision.
There is one very good reason for considering 20/20 to be “normal”, though - since it has been accepted as the standard for over 150 years, most of the human-designed environment has used it as a yardstick for designing visual elements such as roadsigns. The size and shape of roadsign lettering and their placement relative to the road feature they’re describing is all according to a standard that was worked out on the assumptions of (some multiple of) “normal” 20/20 vision, for instance. Likewise for just about every other thing you have to read. So it makes a lot of sense to use that as the threshold. In this sense perhaps it helps to read “normal vision” not as “a normal eye” or “the normal acuity among average healthy humans” but rather “the vision threshold needed to interact normally with the human world”.
Assuming 20/16 is distance low-light you may be over correcting. Your eye needs to accommodate away that correction during close vision, which can cause eye strain and (EndMyopia conspiracy theorists claim) axial elongation and worsening vision.
Full disclosure: I’m an EndMyopia conspiracy theorist.
I hadn’t heard of EndMyopia but it sounds plausible to me. I have been myopic around -6.5 diopters left eye and -5.5 diopters right eye (with astigmatism) for almost 2 decades now. I discussed eye health and preventing worsening / potential training to improve vision naturally with the optometrist (“consulting” optometrist i.e. not part of a glasses/spectacles store, their end product is the prescription values for your eyes). We settled on 20/16 near vision and “20/30ish” far vision (20/30 line easy, 20/20 all correct but with slight effort / hesitation) as a good compromise for my lifestyle - essentially, something that would give me adequate vision for driving and optimal vision for working at a computer. I use soft contact lenses because I was told these use more of the eye muscles for natural accommodation than hard lenses or glasses, thus keeping the eye healthier. I was told to keep a close eye (heh) out for any fatigue or eye strain and I haven’t experienced any of that (although I also didn’t experience it with glasses, so it might not mean much). I had four visits in total over about five years and we saw no change so the optometrist said she was comfortable that my eyes weren’t deteriorating. All of this is over a decade ago and I’ve just been using the same prescription since with no issues, so my memory might be incorrect or some of the science of what she told me might now be out of date, but I haven’t experienced any issues so it seems to be working for me. Not medical advice etc.
How did I just randomly find this? For the best conspiracy theories EM is based on, Google Scholar for clinical research. scholar.google.com, type in 'pseudomyopia', also try 'NITM' and for the most fun, 'lens induced myopia'. Doesn't make EM right, but the optometrists don't tell you what actually cases myopia.
>The 10600 pixels over 20 inches corresponds to 530 pixels per inch, which would indeed appear very sharp. Note in a recent printer test I showed a 600 ppi print had more detail than a 300 ppi print on an HP1220C printer (1200x2400 print dots). I've conducted some blind tests where a viewer had to sort 4 photos (150, 300, 600 and 600 ppi prints). The two 600 ppi were printed at 1200x1200 and 1200x2400 dpi. So far all have gotten the correct order of highest to lowest ppi (includes people up to age 50). See: http://www.clarkvision.com/articles/printer-ppi
I have no idea why everyone forgot how shit 300dpi printers were and how much crisper 1200dpi looked.
It’s often claimed the human eye can’t see above 300 PPI; this is even more misleading than the claim that the human eye can’t see above 30fps (we all know there’s a distinct visual difference between 30fps and 60fps, and most people are able to detect the difference between 60fps and 144fps as well). The PPI limit of the eye depends on how brightly lit the subject is and how far away one is viewing it; for a real upper limit you might use something like the maximums of https://lobsangstudio.com/ls_pixel.cfm which says at 6 inches viewing distance under 10,000 lux (bright sunny day), the eye could go as high as 1200PPI. The fact that microLEDs offer the potential to go beyond even the maximum of generous estimates in best conditions is very exciting, it’s like Formal Proof version of Retina rather than the current Good Enough.