This paper explores textual norms in Finnish subtitling both in theory and in practice. Toury's ideas on translation and norms are first discussed briefly, and invisibility, readability and faithfulness to the original are then identified as the principal textual norms associated with subtitling in Finnish extratextual sources (guidelines to subtitlers and the like). The reality of subtitling is approached from the viewpoint of and difficulties in translating humour. Maintaining the invisibility of the subtitles can be difficult or even impossible because the image itself carries audial and visual cues that limit a subtitler's choices. Breaking norms can also result from a conscious risk taken by the subtitler, the motivation being that a source-culture oriented translation solution cannot communicate the humour of the original to the target-culture audience.