I own the Swift Audubon 820 ED binocular and I am very happy with it. I am especially impressed with the brightness and 3D effects after spending time using a roof prism binocular. However, my question is this: Since it is still possible to find a Nikon 10x42 SE porro on the market, would I notice any significant gain in magnification with the Nikon over the Swift Audubon? I understand that most would regard the Nikons to be a higher quality binocular but I am wondering whether the extra magnification justifies the $800-900 cost.
I have compared both bins side by side, and it's apples and oranges. It depends on your application and personal preferences.
The eyecups on the 820s didn't allow me to see the entire FOV because their large size wouldn't fit into my deep-eye sockets. I probably could see about 6.5-7* with them, still a gain over the SEs, but I lost DOF.
The focuser bridge also flexed on my 820. My solution was to buy the older 804 model for the backyard, and the 8x32 SE, which is lighter and more compact, for carrying in the field.
I found the 6* FOV of the 10x42 SE too restricting.
According to Steve Ingraham, formerly of BVD, the 10x SE and 8.5X Audubon have nearly the same resolution.
An optics "expert" on Cloudy Nights recently called Ingraham's methodology "flawed" so this throws doubt on the boosted resolution numbers Ingraham posted (3.5 arc seconds for the Audubon, 3.58 arc seconds for the SE).
However, my own eyeball comparisons agreed with Ingraham's and RichT's. The two bins look very close in resolution. At longer distances, the larger image scale of the SE would probably be more pleasing to the eye.
But for all day birding, the 8.5x is less fatiguing, and as Ingraham stated, over time you see more detail with a 8x bin, because the shakes from a 10x can negate its extra reach or in this case, larger image scale.
You don't know what you're missing until you do a side by side test. A few months back, another member of this forum and I tested my 8x32 SE against his 10x42 SE to read a warning sign posted on a transformer at the top of a telephone pole.
We both could read the sign much better with the 8x32 even though the 10x has a higher resolving power. And the more you use your binoculars during an outing, the more your arms fatigue, and the more shakes rob detail.
So I consider the 10x42 a specialty bin. Good for special circumstances, but not as my primary birding binoculars.
However, if you have exceptionally steady hands or you are willing to mount the SEs, and have a need to look at targets a distance often, the SE could be "Superior."
A better comparison would be between the Audubon and 8x32 SE. The Audubon's resolution is better, but the binocular is rather bulky and even with the reduced weight of the 820 model, it still weighs more than the SE.
The SE is not WP like the Audubon, but it's well sealed and if you don't dunk them or use them in the pouring rain, they will hold up fine.
Brock