Just picked up a BIGMA

[Overread36]

Goonies -was the TC reporting to the camera at the time? If the TC fails to report (as can happen with lenses not made to take them or with 3rd party TCs) the camera will still report the aperture normally (ie not taking into account the 2 stop light loss) and thus you'll keep AF because the camera can't "see" the TC (Af of course suffers because its based on the actual light levels entering the camera and the aperture loss when using a TC is a real loss not an invented one.

 

[GooniesNeverSayDie11]

I am pretty sure it was reporting, but I will have to go back and check. I know that the 7D wouldn't when I slapped the Bigma and a 2X on it just for kicks But I wasn't really expecting it to.