I have difficulty understanding what the transformed image is equivalent to. This makes it feel like the picture was taken at a difference distance and focal length, but[1] it would look different if that were the case because the perspective would be different. Does this have any "physical" interpretation that would make it easier for me to understand? Like, cropping an image is equivalent to changing the focal length; what would this be equivalent to? A type of rectilinear lens?
[1] With the exception maybe for a single plane in focus?
[1] With the exception maybe for a single plane in focus?