A gravitational lens approximately follows a $1/r$-curve, meaning that rays closer to the lensing object get bent more than those away. My question is, wouldn't that shrink any image as opposed to magnify it?
Consider, for example, the sketch below.
The top ray from the star (that reaches the target) has to come out at a lower angle or else it wouldn't be converged by the gravitational lens (it'd go outward as shown by the uppermost ray). This means that the top and bottom ray have to meet at a smaller angle at the target (which would make a smaller image).
Even when you have an Einstein ring, the rings should be thinner than the object by the same reasoning.
Under what circumstances can something get magnified? Is there a circumstance where the area is necessarily larger and brighter?