Why does my C100 MKI continuously autofocus with my EOS 28mm 1.8 lens?
 

Hi all:

Did a shoot at an ad agency today and noticed that for some strange reason, when I mount my Canon 28mm 1.8 lens on my C100, it continuously auto focuses, even when I have the menu set to "one touch"? What gives? Anyone hear of this before? I also have three other Canon EOS lenses and none of them do this. Something broken in the lens or? Am I overlooking something obvious? Had to turn it to MF to get it to quit auto focusing. Kind of obnoxious in the middle of the shoot.