i have the sigma dock and have had to use it on both the 120-300 and 18-35 which were grossly off. after doing focus adjustments on the lenses i have found that they work the same on the 2 70d's and the 40d which i have tried them on. that tells me the problem is with the lens itself and not the camera/lens pairing and also why afma with the camera doesn't work very well with the new sigma lenses, ae frontfocusing close and backfocusing at infinity and everything else in between. i am a big fan of what sigma is doing with the new products but i think this inexcusable and i will also write them and tell them so.