Subtitling spotting rules refer to guidelines used in the process of determining when and for how long subtitles should appear on the screen in a video. These rules are crucial for ensuring that subtitles are clear, readable, and synchronised with the audio and visual content. Spotting rules may vary on the type of content, language, and distribution channel. 

For example, different settings apply when using the BBC Styleguide for Subtitling, the Netflix 'Timed Text Style Guide', or other industry standards.

These are the most common subtitling spotting rules:

  • Reading Speed: Subtitles should allow enough time for viewers to comfortably read them. A general rule of thumb is around 12 to 14 characters per second or 180 words per minute, but it can vary based on the complexity of the language and the target audience.
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  • Duration: Subtitles should ideally stay on screen long enough to be read comfortably without rushing viewers. The duration depends on the number of words, complexity of the dialogue, and the speed at which the characters speak. Generally, subtitles remain on screen from 2-5 seconds (BBC style guide) to 1-7 seconds (Netflix specification).

  • Line Length: Subtitles should have a limited number of characters per line to ensure readability. Longer lines can be harder to read quickly, so it’s recommended to keep lines to around 32-42 characters.

  • Punctuation: Ensure that punctuation is used effectively to segment the subtitles, aiding in natural reading pauses. Apart from introducing the proper reading pace, line breaks between two lines of a subtitle, and breaks between subtitles should preferentialy follow the punctuation marks.

  • Synchronisation: Subtitles must synchronize with the audio and video. Not only they should appear when the corresponding speech starts and disappear when it ends, they should also be synchronised with the rhythm of the edit on a more fine-grained level.
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  • Speaker Identification: When multiple speakers are present, it’s beneficial to identify them in the subtitles to avoid confusion for viewers. Depending on the use case, speaker changes might be marked by colours or by using a dash ("-").

These rules are fundamental in ensuring that subtitles enhance rather than detract from the viewer’s experience, providing access to content for a wider audience.

Limecraft Subtitle Editor settings give the user the control to adapt the spotting rules for the specific requirements of the project.