focal length ratio

例句：

1. 1. The camera's focal length is adjustable, allowing for different shooting angles.
   相机的焦距可调，允许不同的拍摄角度。
2. 2. In photography, the focal length determines how much of the image is in focus.
   在摄影中，焦距决定了图像中多少部分是清晰的。
3. 3. The scientist used a microscope to measure the focal length of the lens.
   科学家使用显微镜来测量镜头的焦距。