therealthings wrote:
Ok so tried with the 500 F4 L USM in bright conditions. AF is unreliable, very unreliable. At first, just like the 70-200 F4 L (non IS, that Fred put on the list as AF works fine, which does NOT with me) it seems to work fine, until you choose a subject that is much closer or further away. Then you have to manual focus within range to help AF lock on again. But when you turn the zoom on the 70-200, let\'s say from 200 to 150mm and focus, it just bumps the focus back and forth once, and stops achieving focus....
It\'s just pure physics, the phase detection elements are not big enough and far away to detect proper direction when lens is strongly OOF.
