Mike Hitchen , Jan 11, 2010; 06:18 p.m.
I understand that Canon do not calibrate the lens on the camera, but then again they have their owninternal standards so maybe they don't need to (if lens and camera independently meet these standards then they should work together).
Maybe Sigma go one step further and calibrate the lens through their normal processes and do a final check using shots taken with the camera? I twould be interesting to find out. If you get inconclusive replies you could always as the customer services people (though you seem to have had variable experience with them so far).