I broke down and bought a mirror lens. A cheap one. I got a Quanteray 500mm F8. It was cheap enough to try and I have been curious about them since I got my first SLR almost twenty years ago. My camera is a Minolta XTsi. I also bought a T-mount adapter. The lens is very light and compact for a 500mm lens. The only problem is that the camera will not acknowledge that there is a lens on the camera. I have tried program with manual focus, aperture priority and full manual. The lens just isn't returning any aperture information to the camera so the camera thinks there is no lens mounted. A friend that is into Nikon's thinks the problem is that my T-Mount adapter should have a contact on it that matches up to the contacts in the lens mount on the camera to return aperture information. He says that is how a T-mount works on his Nikons. This is my first T-mount lens so I don't know. Anyone have any ideas? I will take the lens back to the dealer Friday but I really want to keep it if there is any way I can use it.