对焦是所有拍摄活动最重要的一环，即使构图失败了，还可以后期裁切弥补，对焦失误了是无法弥补的事情。一般在对焦模式中，主要分为AF-S、AF-C以及MF三种字样，但是对于初学者来说可能完全不理解这些字母代表什么，有何区别。
每年有超过85，000名学生参加该考试。Students study at the medical school campus in Boston’s Longwood Medical Area， and can complete clinicals at affiliated institutions throughout the city. Medical students may also opt for joint degrees， like an M.D./Ph.D. and M.D./MBA， and can cross-register in courses at other schools within the university， including the highly ranked Law School and Business School.
