Below we describe the difference between captions, subtitles on TV and films, and opera surtitles.
A trained captioner prepares the captions in advance so that they mirror the actors’ performance, then cues them live as the action unfolds on stage. The full text of the production appears on the caption unit, along with additional information such as the name of the character who is speaking, sound effects, offstage noises and musical descriptions. The captions appear at the same time as they are spoken or sung, giving deaf, deafened and hard of hearing patrons access to the performance.
Timing of the captions is crucial so as not to pre-empt the actors, especially if the text involves a key punchline or joke. It is vital that the captions do not lag behind the actors because the ability of many people to ‘hear’ the production is lost.
Captions tend to be 'roll-up' rather than 'pop-on' since it allows for more flexibility in outputting as close to the verbatim text as possible.
Television subtitles are generally intended for deaf, deafened and hard of hearing audiences and, whilst character names are not usually given (often because in close-ups it is obvious who is speaking), they are denoted by different text colours. Unlike captions, subtitles are usually edited, and punchlines can appear before they have been spoken.
Surtitles in theatre are for opera and plays performed in a foreign language and will include the English translation (usually edited). They are intended for hearing audiences and features that would be helpful to deaf and hard of hearing audiences, such as character names, offstage noises and sound effects, vocal effects and repeated text, are not given.