noun
aperture ratio
Technical term used in optics, photography, and display engineering to describe the ratio of the effective opening area to the total area.
このレンズの開口率はF2.8です。
The aperture ratio of this lens is F2.8.
液晶パネルの開口率が高いほど、画面が明るくなります。
The higher the aperture ratio of an LCD panel, the brighter the screen.
F-number is the reciprocal of the relative aperture; 開口率 is often expressed as a ratio like 1:2.8.
Compound of 開口 (opening, aperture) and 率 (rate, ratio). A straightforward technical coinage.