Hi! all. I'm helping my friends to take some photos during an upcoming outing. I'm using a Nikon D5000 with Sigma 18-250mm lens. Was wondering how i can lock focus on multiple subjects without some of my friends being out of focus. Cause from the type of focus i can see on my camera, there's the single point focus & also another type that automatically choses the focus points. How should i set my focus in order for all my friends to appear sharp & not out of focus?