noun
Technical term in photography and optics for the ratio of the lens's focal length to the diameter of the entrance pupil. Used when discussing aperture settings.
このレンズの絞り値はF2.8からF22まで変えられます。
The f-number of this lens can be changed from f/2.8 to f/22.
絞り値を小さくすると、背景がぼけやすくなります。
When you make the f-number smaller, the background becomes more easily blurred.