Submitted by György Chityil ... on Fri, 01/19/2018 - 20:34 Hierarchy: NounDescription: {{photography}} The ratio of the focal length of a lens to its diameter; a measure of the light-gathering ability of the lens.Ngram: f-numberNgram Text: f-numberSource: WiktionaryIssue: 0Wiktionary tag: photographyNgram Count: 1