I got a Canon 70D a couple weeks ago from Amazon. As explained here and many other places around the internet, its autofocus system doesn't work as one might think it does. The focus "point" actually covers a large area.
This has led me to many out of focus shots, even when anticipating its modus operandi. It's simply not reliable, no matter how you look at it: When taking a picture of a person looking at you from a top view, ~6m away @55mm, 1/160, 5.6f you'll be lucky to get the face focused. Often times the camera will focus on the grass ground, if it's better lit/contrasted than the face. (The important thing about those settings is that since the face is 6m. away from you it will not cover the majority of any AF cross even if it's dead-center on)
This is very easily tested just staying still and trying to autofocus on the very same spot repeatedly: you'll feel the lens focusing each and every time in a slightly different spot, every time.
I love the camera otherwise, the video is simply awesome and the pictures that come out sharp look simply great. So, I'm seriously considering returning it. I need consistent autofocus. I need to know that when I select an AF point covering a face, the face will get the focus and nothing else will.
I am thinking that a camera with more autofocus points — say, 51 instead of my camera's 19 — will allow more precise selection of the target I really want. But I don't want to spend thousands of dollars to find this out. If you've used both AF systems with a few points and the newer, more expensive ones with many points, can you confirm this? Will more autofocus points make it easier to focus on small targets even when the background is high-contrast?