Tringa,
This argument goes back to my the early days of the forum and beyond, and is one I'd hoped we'd put to bed many years ago.
If you follow the different threads you will be aware that the sharpness of certain binoculars are fairly regularly criticised by some contributors. Perhaps the original Swarovski CL was the highest profile, where dozens on the forum described the view as soft, and was widely ridiculed in the trade. Smaller numbers have complained about the Conquest HD, the Nikon MHG and the Ultravid HD. You might have noticed it tends to be the same group of people? You need to ask yourself, what was the difference that made a higher proportion complain about the CL and a smaller proportion the others. The debate within the forum was pretty heated, but eventually sense prevailed.
It all depends on the comparison between the effective resolution of the binoculars and the visual acuity of the user at specific pupil diameters. Although I would normally report the stopped down resolution of binoculars equating to a pupil diameter of 2.5mm, I think it's clearer if I illustrate it at 2.2mm which would occur at slightly higher light levels.
When the light levels are bright enough to shrink the pupil of the eye to 2.2mm the effective objective diameter of the binocular will be 8x2mm or 17.6mm. If you recall, the Dawes limit for 17.6mm is 116/17.6 or 6.6 arcsecond resolution. There are other slightly varying definitions but is pretty much the same as 5% contrast by MTF analysis and the limit using line charts.
Obviously visual acuity does vary between individuals. The threshold for normal vision is 20/20 ( or 6/6) in metric. This is the average acuity for 65 year old. That is better than 120 arcseconds to the naked eye, or 8 times better at 15 arcseconds with an 8x binocular. 15" is over 2x worse than the Dawes limit for an effective objective diameter of 16mm. I don't know that anyone would test a binocular for sharpness with one eye, so for home testing I would normally do a two eye test. The best result I've measured was 20/9 acuity or 54 arcseconds. With 8x magnification that would be 6.75 arcseconds.
We now have a situation where an individual's magnified resolving power is virtually at the Dawes limit; 6.6" vs. 6.75". I asked that person to compare two binoculars. One was the amongst the best I've tested and at the Dawes limit stopped down, the other was just half an arcsecond worse. Whick would be about tyipical for an alpha. Having tried the worse one first, hand held, it then took him no more than 5 seconds to pronounce the better one sharper. No charts, tripods or boosting, just a look down the garden.
No it wasn't me, it was my son who doesn't own a binocular and might only pick up mine once a year. I had 20/9 eyesight when I joined the forum. It's now 20/11. It still only took me recently a few seconds to realise the new Trinovid HD was poor. These days, the Conquest HD, Nikon MHG and even the new Swaro CL take me a little longer to spot the difference between those and their top of the range bretheren, but then, very few of those are diffraction limited either. I'm sure it wont be long before I need a tripod, a suitable target and have to rely on boosting to spot these differences. But don't forget, there are others on the forum, that have never seen a USAF 1951 chart or attempted a boosted test that see differences even more clearly than I do... or did. :-C
David