F-number marking光圈刻度
coude f-number折轴焦点
effective f-number密效光阑
f-number measuref数测度
F-number焦比;光圈值;光圈系数;焦距比数
f-number spacef数空间
f-number f光圈数;数
overall f-number总光圈大小
f- numberfl数
N（名词） the numerical value of the relative aperture. If the relative aperture is f8, 8 is the f-number and indicates that the focal length of the lens is 8 times the size of the lens aperture 焦距比数 [photog] → see also T-number