Originally posted by SlickYamaha Its not so much a switch, the collar (focus ring) slides back and forth. Back being mf forward being af. This only serves to "turn off" the focus ring spin. When the camera is in af, slide the ring forward and it wont spin, when the camera is in mf, slide it back to engage the focus ring
Then I misunderstood what moving the focus ring back and fourth on the tamron does. I found a YT video reviewing the lens and I thought you could completely turn off AF on the lens. If you cannot keep the lens from auto focusing then you cannot easily use catch in focus with it. With my FA* lenses, moving the focus ring backward or forward, simply disengages the AF mechanism in the lens (when on MF). Seems like kind of a half assed feature on the Tamron if it doesn't work the same way.
Though there is a way but it's a bit of a pain. If you hold the lens release button (I use the Johnny Cash finger, google it) while pressing the shutter release, you can turn the focus ring as a manual focus. The obvious problem and annoyance with that, the AF motor still spins like crazy and it's more of a balancing act than you want to play with.