I recently bought a Rokinon (=Samyang) 300 mm catadioptric lens for use with my Fujifilm x-e1 mirrorless camera. It seems to work OK, but there are two things I don't understand about it:
This review says that "on Fujifilm X and Sony E-mount cameras [the equivalent focal length] is 450mm." What does this mean?
When I rotate the focus ring all the way counterclockwise, distant objects (even several miles away) appear out of focus. To get them in focus, I have to back off a little. The white pointer seems to be under the ∞ symbol when I do this. At full rotation, the indicator is under the symbols m and ft, which are beyond the ∞ symbol. This is very awkward. I normally expect to be able to rotate the lens all the way in order to get a focus at infinity. Am I misunderstanding something? Is this a design or construction flaw in the lens? An incompatibility with my camera? What would be the purpose of having a lens that can focus on a converging bundle of rays, which is something we never encounter when photographing real-life objects without some other optical element in front of the camera? Is there an adjustment that I need to make to my lens?
If the answer to #2 is that I need to adjust my lens, how do I do that?
possibly related: Do I need to calibrate my mirror lens?