A Photographer's Guide to Focus and Autofocus: From Snapshots to Great Shots is here to answer all your questions about the focusing system in today's cameras and their various autofocus modes. Photographer Alan Hess covers the simple basics of focus: manual focus versus autofocus, the best focus modes to use, and how focus works in both DSLRs and mirrorless cameras. Then he discusses more advanced topics, including autofocus sensor types, back-button autofocus, and focus for DSLR video.