It's in one of the AF menus, second or third, I think. I have mine on the first setting.
Thanks neuro, I'll check my menu when I get home. I looked up the user's manual online and it says there are three options for USM lens electronic MF:
Option 1. ON: Enable after One-shot AF= After AF operates, if you keep pressing the shutter button
, you can focus manually.
Option 2. OFF: Disable after One-shot AF= After AF operates, manual focusing is disable
Option 3. OFF: Disable in AF mode= When the lens' focus mode switch is set to (AF), manual focusing is disabled.
Reading the manual makes it also seem like you have to keep the shutter button (or in your case the back focus botton) pressed to manual focus while the lens is set to (AF). Again, maybe I am just reading it wrong. Not to doubt you, but you are sure
that if you just turn your camera on, don't press any bottons and turn the focus ring on the lens while set to (AF) that it will manual focus? I just want to make sure there is nothing wrong with my lens, or yours for that matter