Quote Originally Posted by Lex Jenkins
At the risk of thread drift I'd consider my sense of vision - and by that I mean with my nekkid eyeballs - to be akin to a well corrected 17mm lens (for 35mm film format) with heavy spherical aberration.
If that sounds peculiar, consider that most of use have very good peripheral vision that matches an ultrawide very closely. Yet we can only clearly see whatever we're actually looking at. Hence the reference to spherical aberration, which in a lens diminishes the clarity at the periphery of an image.
It doesn't sound "peculiar", but it would apply to "field of vision", not "perspective" within that field. That human central vision has more clarity is due to two major reasons; the distribution of rods and cones in the retina of the eye, and the ... I was about to write "psychlogical" .. but that is not quite correct ... uh... "Visual Preconditioning", where the information in the center of the visual field is more important, therefore we are conditioned to pay the most attention to it.

Hmmm... "heavy spherical abberation" ... I don't think I have that in *my* vision... but I'm not sure I'd notice it if I did... the brain can correct all sorts of optical "strangeness" through experiencing and conditioning to make the end result "correct" ... perceptually correct.

That the "normal" lens has a focal length equal to the length of the diagonal (or diameter) of the field is a more or less arbitrarilly choen value... at that focal length/ field diameter, quite a few optical design problems are minimized - that is why "Normal" lenses can have the largest maximum apertures.