An honest starting point
Subtitles are a visual feature. They are text drawn on a picture, meant to be read by eyes. That makes them a poor fit for viewers who are blind and an imperfect one for many who have low vision. It would be easy to write that subtitles help everyone, but for this group the more helpful thing is to be clear about where they stop working and what to use instead.
Visual impairment is also a wide category. It includes total blindness, low vision, color vision differences, sensitivity to light, loss of the central or edges of the visual field, and fluctuating sight. Needs differ accordingly. This article is general information.
Blind viewers
A blind person cannot use subtitles drawn on the screen. For them, the spoken audio is the primary channel, and what they are missing is the visual information: who has entered the room, what a character is doing, what is shown in a chart.
The main support here is audio description, which adds narration about important visual elements in gaps between dialogue. It is a separate topic with its own conventions. Subtitles have only a minor role, with a few exceptions:
- Foreign-language speech. If a film or video has speech in another language, subtitles are how sighted viewers follow it. A blind viewer needs these read aloud, or voiced over, or the content dubbed. Some audio description tracks include spoken subtitles for this reason, and dubbing options can be a better fit than reading.
- On-screen text. Titles, names, dates and captions in the picture are visible text that a blind viewer would not know about unless description or audio covers them.
- Transcripts. Written transcripts that include description can be read by a screen reader, which converts text to speech or to braille. This makes subtitle text available in another form when it is supplied as real text and not just an image.
That last point is worth stressing. Screen readers can only read text that exists as text. Subtitles baked into the video image, as in burned-in subtitles, are invisible to them. Separate subtitle tracks and transcripts are far more accessible.
Viewers with low vision
Many people with low vision can still read, but they need text that is larger, clearer or easier to separate from the background. Here the quality and flexibility of subtitle display make a real difference.
Size. Larger text is often essential. Some viewers need it far bigger than typical defaults, and some need to sit closer to the screen or use a magnifier. Viewer-controlled size is far more useful than a fixed size.
Contrast. Strong contrast between text and background helps. A solid or semi-transparent background panel behind text keeps it readable over bright or busy scenes. This is a central part of subtitle legibility.
Color choice. White or yellow text on a dark background is common. Some people with color vision differences find certain combinations hard to tell apart, and some with light sensitivity prefer reduced glare. Because needs vary, adjustable color settings are better than a single fixed scheme.
Font. Plain, clear fonts with good spacing are generally easier. Decorative styles, thin strokes and heavy italics tend to be harder.
Position. Some viewers find it easier to read text in a particular part of the screen. Being able to move subtitles can help, especially for people with a partial field of vision.
Pace. Reading with low vision is usually slower and more tiring, so fast subtitles are less usable. A calmer reading speed helps, as does the ability to pause.
Using a screen and its settings
Many televisions, phones and players include options to enlarge text, change color or add a background. The device settings menu is the first place to look, and subtitle appearance controls can make an otherwise unreadable default usable. For people whose sight is changing, it helps if these settings are easy to find and remember.
Combined needs
Some people with a visual impairment also have a hearing loss or other difficulties. In these cases, audio description, captions and transcripts may all be useful, and a sensory impairments approach considers them together. Deafblind viewers in particular may rely on text sent to a braille display.
What producers can do
- Supply subtitles as a separate, restylable track, not only burned into the image.
- Offer audio description for content where visuals matter.
- Provide a transcript with visual details included, in an accessible format.
- Read important on-screen text aloud in the narration where practical.
- Avoid conveying information by color alone.
An accessibility statement that says what is available, and where to ask for something else, helps viewers know what to expect.
Requirements differ by country and sector, and they change over time. A qualified professional or the relevant authority can advise on what applies.
Summing up
For viewers with visual impairments, subtitles are secondary: valuable to some with low vision when they are large, clear and adjustable, and mostly unavailable to those who are blind unless the text is also presented in a non-visual way. Real access comes from combining readable subtitles with audio description and accessible transcripts, and from letting the viewer choose.