Major Autofocus Problems with Sigma Lenses (Glitch) 4,031

In this video, we'll be taking a look at a major problem with Sigma lenses - sporadic and inconsistent AF when using the IR AF assist beam present on most flashes (mine is the SB-910).I've linked some further resources here which explain the same problem - it is not unique to my body or lenses.http://www.dpreview.com/forums/thread/3370545 http://photo.net/nikon-camera-forum/00bRoM http://www.fredmiranda.com/forum/topic/1180988/1