You got to watch research, particularly if they say they are not finding something, because it is easy to muck up research. What we know is proven, is human vision sees 8k, if somebody doesn't that's their issue. There are books like "How to prove your eyesight without glasses". In it they mention, people might be looking concentrating on an area outside there maximum vision, which they can look for and find and retrain themselves. I did it to maximise vision apart from other visual issues.
Now, on mucking up research making a poor 4k resolution print and downscaling to a good 2k print, then comparing, would not be a good acquisition comparison. The 4k or 8k downscaled to 2k is expected to look better then a pure 2k window out of the same camera.
Now, comparing it on a 50 inch or so TV at conventional distances, on a small field of view, is just wrong science. Resolution has all to do with field of view, as that is how it works in human vision. Filling out the inner peripheral vision zone, so you don't have to look around, is a good field of view to use.
Years back people used to have such small TV's and sat at such great distances Standard Definition looked good, but the images looked small. I remember Fist, was it in the Australian decades ago, complaining his he was going fit an upcoming massive wide-screen into his living room (probably around 40-50 inch ha, ha compared to now days
). He was getting the placement information wrong in screen width rather than hight too, so I think he was concerned about how far back he had to sit and his small it looked etc. But, as you can see misunderstandings don't help debate. So, what happened with SD is they wanted bigger TV's where the closeup and now mid range shots look at least life like size (the more the merrier, which is cinema territory) going towards long shots. You sit close enough so you can still see this full screen without looking around st what's happening, but not closer then your short range vision. So just over 6 feet on something like a 70 inch to 80 inch screen (sorry, I've firgittennthe exact measurements, but around 60-70 degree arc of vision. That's where you should to 2k-8k comparisons.
Now, there are a few more important considerations in comparison. The lower the contrast difference between two pixels, the less you notice the resolution, and at the sane time, the brighter images of an emissive display may result in less visible resolution. Once you look up all the research on this, and setup, you are right for an actual optimal comparison to get better results.
As for acquisition, the same lens, camera, framing, lighting and set up on a good 8k camera. Using 8k, 4k and 2k sensor window modes, film the same resolution chart, carefully adjusting lighting evenly accross the chart to compensate for moving tjr camera and change of aperture as you move the camera further away, for the 4k and 3k framing, keeping the average angle of rays similar. For this Bayer sensor is probably best, as it is the common one. As you can see, this may take weeks to figure out properly, so that difference between esxh shot I'd mainly only the resolution, which takes put lens effects. Don't just use a scsmed chart file, as this will lead to rnhsnvent onntjr downscaling, or different resolution charts.
The tricky bit, use a top quality calibrated 70+ inch display that you can turn all image and scaling enhancements OFF. Now you might be ready to display the 8/4/2k image files on the thing at the precise calculated viewing distance. Remember also to optimise room lighting like a grading studio would, adjusted for your distance. Now you can test your eyesight. Some people won't notice much difference between 2k and 4k, increasing with age. Some people will notice the difference between 4k and 8k increasing with the decrease in age. So, the kids with good eyesight in their teens, maybe younger, should notice the difference and see further down the chart. You could try an eyesight test, but the best would probably be a checkerboard pattern of black and white squares, like I use, and move further or until you can tell the difference between them, and then clearly the difference. Another I try, is two lines one pixel thick, one pixel apart, in each direction, forming a cross. The different resolution patterns and crosses could fit on one screen. Of course, by 2k, 4k and 8k, I mean 1920, 3840 and 7680, as that's the displays we can readily get. 8k will still have the minor disadvantage of the pixel cell structure interfering with the test, where it's more averaged out at 2k. That's the simplified test. In the real world, the lower contrast scenes, movement, and the people not concentrating on areas of more visible resolution will make differences less apparent. However, the lens sculpting of the image should have more effect, and the image look clearer (putting aside noise).
BM could do such a display at NAB to should off 8k camera benefits, and how much better 8k downscaled to 4k and 2k looks, as a promotional gimmick for people to test hows good their eyesight is. Of course, it is best a corridor walk by and stand on this line to see sort of situation and you have to have it adjusted and pre tested to suite floor lighting and visual accommodation as people look around from other things to the test and their brightness adaption kicks in. Sine screens if actual images and footage done to the same standard might show a more positive difference for those who can't see 8k, and screens using good 8k downscales to 4k and 2k compared to 4k and 2k sensor windows from the sane camera. Then people get three shits of marketable benefits of 8k. One, yes I can see it, two even I can't it looks nicer and clearer, and three even if I can't it sure names nicer 2k (and if you can't you may need better glasses). People will be talking about it for days, and mentioning it for weeks and months. There was something you needed a loupe for in setting it up, but I forget.
A full audience is not just you, but everybody that comes to a screening with whatever visual capability.