Like Henry, I've done a lot of side by side comparisons of different binoculars, estimated both full objective and stopped down resolutions value, and noted significant variation in perceived image sharpness
Henry mentioned my visual acuity was a bit better than his, but l still found my magnified and unmagnified acuities often corresponded exactly, meaning the effective resolution is eyesight limited (though there have been a number of notable occasions where the binocular was limiting). Where where my eyesight is the limiting gactor I still find clear differences in apparent sharpness which appears to correspond exactly to the stopped down resolution.
I should point out these distinctions will be increasingly difficult to detect as the gap between the instument and the eye's effective resolution increase and it probably helps to have well developed perceptive skills too.
I've bench tested something over 20 different binoculars with objective diameters between 30mm and 56mm and
I have found absolutely no relationship between objective size or exit pupil diameter and effective optical performance. The best I've found for both effective resolution and perceived sharpness were an 8x32 and a 12x50. My worst binocular by some margin was a $30 10x42, and as far as I recall, when boosted, it wasn't anything like as bad as Henry's image for the 8x30 Habicht. I think there might have been a technical issue with that photo.
I'm not as young as I once was, and I'm more dependant on good light conditions to judge optical quality than I used to be. Thinking back over various visits to Birdfair and different retailers, I've probably looked at 400-500 different binoculars when my eyesight was firing on all cylinders. They would have ranged from 8x20s through to 20x80s. I'd guess perhaps 20 or so really wowed me at the time, and I suspect might have matched the Dawes limit. That means they would have been essentially aberration free stopped down. That would have included some alphas, but some mid range and at least three budget binoculars would make that list. Rather more, including some from the big three companies, have been clearly optically limiting.
I should point out that resolution by no means the only factor to control image quality, and others may have different priorities.
David
PS. I should have mentioned that I have tried the 8x30 Habicht on three occasions. My opinion at the time was that was that the resolutions of those samples were good, possibly around 125-130/D, but definitely short of the Dawes limit. In my opinion they were all further impaired by a diffuse stray light issue.