Hello, here is my question: if an object position can only tend to infinity, without ever reaching it (since infinity is just an abstraction), its image will tend to appear on the back focal plane of a converging lens, without ever forming there. The image will always be created on the image plane, infinitesimally far from the back focal plane. If the object is instead placed exactly at the focal length (that is feasible), its image is said to be: upright, with finite magnification, and forming at infinity! We all know that to view a virtual image we extrapolate the path of the rays. If the image is at infinity the rays from each obj point are all parallel. The eye can be relaxed in viewing that virtual object. But we also know that if we look inside a simple magnifier (with object at f) the image appear to be some finite distance inside the lens, and not at infinity. Where is the flaw in my thinking?