I am having trouble getting my camera to focus on what I want it to when I want it to. When I zoom in to focus on someones face, it almost always focus' on the background. I press the button halfway to try and get it to focus on something else but it doesn't work most of the time. Is there an easier and faster way to get the camera to focus on what I want it to? I'm getting quite frustrated with it not doing what I want it to do.