It looks like the Tamron is front-focusing, just a little bit. The 70-200mm is back-focusing, not horribly but definitely noticeably. The Tamron'sfront-focusingis unlikely to substantially affect images, but the 70-200mm'sback-focusing will probably have an effect in critical focusing situations, (wide open with a close subject).


It's this sort of thing that AF Microadjustment is designed to correct.