series of f-number

例句：

1. 1. The camera has an f-number of 5.6.
   这台相机的光圈数是5.6。
2. 2. The photographer used the f-number to control the depth of field.
   摄影师使用f数来控制景深。
3. 3. In photography, the f-number determines how much light is let in through the lens.
   在摄影中，f数决定了通过镜头进入的光量。