a lens that adjusts automatically的用法和样例：
- A line through the optical center of a lens that is perpendicular to both its surfaces.
- A lens that falls short of this ideal suffers from drastically degraded resolution.
- For a lens that's likely to be sitting on your camera most of the time, you want performance, and the 17-55mm appears to deliver it in almost every repect.
- This article provides the basics of what you need to know regarding MTF charts and provides a comprehensive method for helping you choose a lens that will best suit your needs.