问:有的摄影镜头上标明其最大光圈为一确定数值(如F4),也有的摄影镜头标明的最大光圈为一变动范围(如F3.5～4.5),二者有何区别?如何正确使用? 答:调节变焦距摄影镜头的变焦环,可使该镜头的焦距值产生连续变化,由公式(1)可知,当摄影镜头的焦距改变时,必将引起该镜头F数或入瞳直径D产生相应变化。根据变焦过程 Q: Some photographic lenses indicate the maximum aperture is a certain value (such as F4), and some photographic lenses indicate the maximum aperture for a range of changes (such as F3.5 ~ 4.5), what is the difference between the two? How to correctly use A: Adjusting the zoom lens of the zoom lens can make the focal length value of the lens produce continuous changes. It can be seen from the formula (1) that when the focal length of the photographing lens is changed, the F number of the lens or the entrance pupil diameter D Produce the corresponding change. According to the zooming process