noun
effective sensitivity; functional sensitivity
Technical term used mainly in photography and imaging to describe the practical light sensitivity of a film or sensor, as opposed to its nominal rating.
このフィルムの実効感度はISO400相当です。
The effective sensitivity of this film is equivalent to ISO 400.
デジタルカメラでは、実効感度を調整することでノイズを抑えられる。
With a digital camera, you can reduce noise by adjusting the effective sensitivity.
Compound of 実効 (effective, practical) and 感度 (sensitivity). The exact historical derivation is uncertain; the term is a modern technical coinage.