Suzanne-- Are you sure about that? I'm sitting here reading your post, looking directly at the laptop screen. Yet in my peripheral vision, I see the windows behind and to the sides of the screen, the outdoors beyond them, the bookshelves on both sides (inside the room), the rest of the desk, and part of the floor. Surely, I am CONCENTRATING on the screen, but isn't it my brain that is doing the concentrating, and not my eyes? My eyes are indeed focused (in the optic sense, not the conscious sense) on the whole view, but isn't it my brain that narrows my attention to the screen and keyboard?
Caveat: I am not a psychologist, nor an ophthalmologist, so this is not a rhetorical question; I really don't know the answer, but it seems to me that the eye, as an optical instrument, must be focused on everything in its view.
Eddy.. I could be utterly wrong!
Like you.. I'm looking at the screen of my computer as I write this... watching each letter as it appears. When I am focussed on one point, the rest is a bit of a blur... I can see green out the window behind the computer... but I'm not really making out the individual trees and leaves that are there. It's difficult to take in all the details of any scene in front of us (especially the mess on my desk... wish that would just disappear from view

)/ I can look at all the details... just not at the same moment.
When I review film... and print pictures, there are things there that I overlooked. I tend to concentrate on the perimeter of the frame when I am shooting. In the following photograph... I knew I had a bright spot of sun behind my child... I knew he was holding (though I could not see it, so my brain fills in that detail) a gill snail that was in the bucket... but I did not consciously see the shadows of leaves on his shoulder blades.
(there was a url link here which no longer exists)
It was a pleasant surprise, and admittedly, easier to see in the print than the scan, but I think that's what I mean by a camera lens (with film of course) can record the kind of detail all at once, that is hard for our eyes to see at the same time.
That's why, I think, taking the time to hone our observational skills will improve our pictures... if for no other reason than, we can find ourselves in situations to make those happy accidents and details happen more frequently... even if our eyes behave slightly differently than a camera lens.
If that makes any sense at all??
Oh, and Bethe... great avatar!!! Good to "see" you again!!