Rules for text in videos

Text overlays

In general terms, the rules already outlined above also apply to animated videos with text, text overlays and animated texts on real-image videos. They are summarised again briefly here together with some additional guidelines.¹

Typefaces

Dynamic sans-serif typefaces such as Calibri, Verdana, OpenSans, Noto Sans and Frutiger are recommended.

Specific suggestions relating to typeface, stem width, type width, intercharacter space and notation are provided in the relevant sections.

Font size should be chosen to ensure that it is sufficiently large to be seen in a video in full screen mode on an average smartphone screen at a normal reading distance. For full HD videos with a resolution of 1920 x 1080 pixels, this gives a minimum font size of 40 to 60 pixels for body text. Titles should be at least 50% larger than body text.

This section explains how to precisely calculate which font size to use depending on video resolution and screen size.

Calculating font size for text overlays – an example

If a video with 1920 x 1080 px (full HD) and so a diagonal of 2203 px is to be displayed on an average smartphone in full screen mode, the 2203 px diagonal must fit on the (average) 6.174” diagonal of the smartphone. In mathematical terms, this gives a resolution of 357 ppi (2203 px / 6.174” = 357 ppi). This (virtual) resolution can be entered in the Font Size Calculator (in ‘smartphone’ mode) to give an accurate font size recommendation, though it will only relate to an average value, in this example, to the resolution or diagonal of a full HD video.

Lower (HD-ready 720 x 1280 px) or higher (UHD 3840 x 2160 px) video resolutions will result in proportionately larger or smaller font sizes.

Example:
Reading distance: 40 cm
Visual acuity: 0.5 (visual angle 18.2')
Ratio of x-height to font size (e.g. for Frutiger): 0.51
Virtual resolution for full HD: Root ((1920 px)² + (1080 px)²) / 6.174” = 357ppi
Font size: 58 px

Text volume

A line of text should contain no more than 30 characters, and no more than 3 lines of text should be displayed at once.

Dwell times

The minimum dwell time is 13 characters per second. That means that a line of text comprising 30 characters should be displayed for at least 2.3 seconds. The more sophisticated the animation and the faster the previous image content or cutting speed, the longer the dwell time should be. Videos for children should also have longer dwell times.

The minimum interval between two subtitles is a frame (i.e. 1/24 sec, 1/30 sec, 1/60 sec, etc., depending on the frame rate). This means that subtitles should not immediately follow one another but instead be separated by a perceptible visual break.

Position and alignment

Where possible, text should always be placed in the same position on the image. It should preferably be placed at the bottom of the image unless this covers other important text or image content.

A woman with dark hair and a black coat walks through a park with a long cane and a badge for the blind. Dark green bushes and other walkers in dark coats can be seen in the background.

Contrast

As a general rule, you should ensure clear contrast between text and background. Text should not be placed on a cluttered background or on colour gradients. Where necessary, the text should be placed on a clearly contrasting colour field. Black text on a white background (or vice versa) provides optimum contrast.

Red and green combinations and contrasts using complementary colours should be avoided. For other colour combinations, see the Contrast Calculator.

Use colour changes during a video sparingly. Avoid contrast and colour changes during a frame.

Text animation

As a general rule, text animation should be discreet and use the same type of animation to ensure that the text always appears in the image in the same manner. Movement should be right to left, corresponding to the direction of reading.

Dwell times for animated texts should be calculated to ensure that the text remains motionless for the minimum dwell time of 1 second for every 13 characters.

Further information on accessible videos can be found on the hoerfilm.info website.

Summarized Recommendations
Rules for text in videos

Follow the recommendations on typeface, spacing and notation given in Section 1. Characters
Font size for text: approx. 40 to 60 px
Text volume: max. 30 characters per line, max. 3 lines
Dwell times: 1 second for every 13 characters, i.e., at least 2.3 seconds for a 30-character text line
Where possible, text should be placed at the lower edge of the image
For optimum contrast use white text on a black background (or vice versa); for other colour combinations see the Contrast Calculator
Use text animation sparingly; text should preferably move from right to left (in the direction of reading); allow adequate dwell times

Footnotes

↑ Empfehlung für Standards barrierefreier Filmfassungen der Filmmförderungsanstalt FFA, 2017

Untertitel-Standards von ARD, ORF, SRF und ZDF, 2020

Fokusgruppe des Deutschen Blinden- und Sehbehindertenverbandes e.V., 2022