I'd like to first start out by thanking another Photo.net subscriber, William W. who helped a lot in the portrait forum. My question here pertains to the camera I'm using and an issue I was running into during one of my first portrait shoots. It was an outdoor session, I had the couple riding a bicycle at times and just generally letting them interact with each other. I was using my D7000, I rented a Sigma 85mm f/1.4 and was having trouble with the lens auto focusing on the faces/eyes. I switched to manual focus but even with slow walking around or even just posing it was too slow to get the focus point where I wanted it and then focus meter etc.. Are there other Nikon bodies that would do a better/faster job at getting focus on the face/eyes? I look at the mirror less bodies like GH4, EM-1, with touch focus and wonder?