No. It is because the F1.7X has its own moving glasses to achieve AF. Since the travel distance is limited, pre-manual focus is required for telephoto lenses.是什么意思_No. It is because the F1.7X has its own moving glasses to achieve AF. Since the travel distance is limited, pre-manual focus is required for telephoto lenses.在线翻译_英语_读音_用法_例句