Originally Posted by hellosailor
"The exit pupil is not on the retina. It has nothing to do with the retina. It is is the same position as the eyes pupil (technically slightly incorect, but close enough without confusing the issue)"
I understand that. But in this context, all eyeballs are the same size and all retinas are the same size, and that puts them all in the same position/geometry in relation to the exit pupil of the binocs. If the binocs had a 50mm wide exit pupil--it wouldn't matter because the iris would cut off the image at ~6mm and the retina can only accomodate a certain image size, no matter what angle the image entering the eye is "expanding" to.
The size of the retina is a limiting factor. The length of the eyeball is a limiting factor. The size of the iris is a limiting factor. The exit pupil size is another limiting factor--and the only relevant one that can be changed by the binoc maker, within limits.
The exit pupil does not limit the field of view.
Nor does the size of the retina, or the size of the iris.
The whole of the FOV passes through each point in the exit pupil. The exit pupil and/or the iris could be made minutely small and the FOV would be unchanged (but the image would be very dull)
The binocular manufacturer can modify the FOV without altering the exit pupil size.