noun
a number that shows the relationship between the focal length of a camera lens and its diameter
••
WORD ORIGIN
early 20th cent.: from f (denoting the focal length) and number .
noun
a number that shows the relationship between the focal length of a camera lens and its diameter
••
WORD ORIGIN
early 20th cent.: from f (denoting the focal length) and number .
Oxford Advanced Learner's English Dictionary. Оксфордский английский словарь для изучающик язык на продвинутом уровне. 2005