>>3188268The distortion you’re talking about is perspective distortion, and it really is just a function of crop.
You can see this with your piece of paper example. Go out to a road where there’s a bunch of evenly spaced telephone poles. Look through your paper hole with the hole close to your eye. Things look just like they do with your normal eye. Because it’s your eye.
Now move the paper away so it’s surrounding a smaller, farther-away portion of the world. See how the telephone poles through that hole look like they’re closer together?
It’s easier to see with telephoto distortion since you can’t make your eye take in a wider-than-normal perspective, but wide angle perspective (rectilinear wide angles, not counting fisheyes which is a different type of distortion) is just the flip side of that coin.
Which means, a normal lens on 35mm is NOT a wider field of view than a normal on medium format. They’re both normals, and will give the same normal perspective. Using your paper example, leaving the paper in the same place and cutting the whole bigger is just like using a larger sensor with the same focal length—like using a 50mm lens on a medium format camera, for instance. It’s no longer a normal, it’s now a wide-angle, and it’ll give you wide angle distortion.
