(reposted for clarity without formatting symbols, LOL!)
Distinguishing apparent FOV from optical persective is needed to understand what is going on. Also what signals to the brain 3D info (beside color, mist and blur).
Here's again as simple as I can write it a summation of where we are:
1. Image taken at same position with wide angle versus telephoto lens of subjects at some mid distance, say 10-50 ft.
a) Angle ø degrees subtended at the lens front element at the central axis is identical for all focal lengths as it only depends on the ratio of the distance to the subject and the diameter of the detail being observed.
b) The perspective on the film plane is defined by angle ø and is never changed by cropping.
c) Only the apparent field of view changes when the image circle is not fully used.
c) So, only the apparent field of view and apparent angle of view are altered by cropping. What would be included in a human's field of view is the "normal" field of view for a lens. Cropping an image mimicks this, but doesn't change the perspective of how 3D images are rendered on the flat image plane, since the capture angle ø is unchanged!
d) One can take the center of the wide angle image and enlarge it to overlay the image taken with a telephoto lens and they will be geographically close to identical. However, they will differ in contrast, depth of focus and 3D effect depending on lens quality and aperture and ratio of diameter of object and distance to the
object.
Thus difference in this quality will be more apparent at
wider apertures closer to the camera but will vanish at infinity (eg images taken of the moon at f11).
2. Image taken at distances such the subject fills the frame with
either a wide angle lens or telephoto lens
a) The image taken with the wide angle lens will be very close to
match the field of view captured on the sensor with the telephoto lens.
b) The wide angle lens image will cover the same amount of the subject but will have an angle ø which is much larger than our previous angle ø where BOTH images were taken from the SAME
distance from the subject.
c) The larger angle ø means that the perspective of the image
taken with the wide angle lens, is now distorted compared to
the previous image pair, where the camera to subject distances were identical.
d) This distortion caused by the new and larger angle ø and cannot be altered by cropping the image.
At close and medium distances, the image with the wide angle lens will always have more separation closer to the camera and less compression of sequential subjects at progressive distance from the camera than images taken with the telephoto lens.
The latter will progressively compress more distant subjects.
At infinity, the compression effects will tend to equalize and
pictures of the moon will have closely similar compression effects with all our lenses.
Wide angle lenses tend to have greater depth of field and less compression and therefore look more 3D.
Telephoto lenses have narrower plane of focus, include less information about the environment, have less adjacent reference point for depth signals to the brain, and so a perceived as flatter.
In all these conditions, cropping does not alter distortions, depth of field, bokeh, contrast or perspective, just "apparent" field of view.
If one crops a wide angle image to the real field of view of a human, then that portion of the image plane may masquerade as the normal field of view, however, the perspective will always be dependent on the angle ø that any subject makes with the camera based on merely the subjects diameter and distance form the lens.
Asher