having bought a d3100 i thought i would buy some better lenses so i bought a Tamron SP 500mm f/8 Lens with adaptall 2 nikon fit i connected the lens to camera but it says lens not connected this was in auto so i switched to manual and tried to set the f stop to 8 but it would'nt let me now the person i bought it off had a d5000 i'm wondering if its the wrong adapter for my camera .......any suggestions would be welcome.......cheers...