焦距比数

例句：

1. 1. The camera has a focal length of 50mm.
   这台相机的焦距是50毫米。
2. 2. The photographer adjusted the lens to get a better shot.
   摄影师调整了镜头以便获得更好的照片。
3. 3. The film's exposure was determined by the camera's focal length.
   胶片的曝光程度由相机的焦距决定。