The question may seem simple, so let me explain it more:
I had a Canon T2i, which I used for a time with my fish eye lens. When zoomed all the way out on the fisheye lens there used to be visible in the corners black space (the fish eye image is circular and so the sensor would capture the areas outside the circle as black space). This effect was desired.
Now I am using a Canon T3i with the same lens, but on this camera when the lens is zoomed all the way out there is no area outside of the circle visible in my photos, as if the sensor is closer to the lens or something and simply can't achieve the same level of zoomed-outness. The entire circular image fits within the frame, there is no negative space captured as with the T2i.
This seems a little odd to me, I assumed these two models were relatively similar but this difference seems pretty dramatic to me, and I don't have a good explanation as to why it is this way nor do I know if there is anyway I can correct it. Is there a way I can use the T3i with the fisheye achieving the same effect as the fisheye on the T2i? Do I need to buy a real full-frame camera?