aperture ratio; relative aperture
Technical term in optics and photography; the inverse of the f-number (Fナンバー). Used to describe lens brightness.
See also: Ｆナンバー
The aperture ratio is a value that indicates lens brightness.
The larger the aperture ratio, the brighter the lens.
Compound of 口径 (aperture, caliber) and 比 (ratio). A straightforward technical term.