Accessible PowerPoint (implementation guide)

4.9. Contrast ratio of texts

Texts have a sufficient contrast ratio to the background of at least 4.5:1.

What is meant by this?

The contrast ratio in PowerPoint refers to the ratio between the brightness of the text and the background on which it is displayed. A high contrast ratio makes the text easier to read. A sufficient contrast ratio is achieved when the text colour stands out clearly from the background colour. The contrast ratio for normal texts is at least 4.5:1. Black text on a white background (or vice versa) represents the optimum contrast. If other colours are used, the contrast ratio must be checked.

Why is it important?

A sufficient contrast ratio between text and background colour is of great importance, especially for recipients with impaired vision. If the contrast is not high enough, the text can be difficult or impossible to read, resulting in barriers to the approval of information.

For example, recipients with colour blindness have difficulty distinguishing between certain colours. A sufficient contrast ratio helps to ensure that they can still read the text. If the contrast ratio between the text and the background is low, it can be more difficult to read the text, even if it is large.

Sufficient contrast not only makes it easier for recipients with visual impairments to perceive content. Recipients who work in an environment with poor lighting conditions, have a printout in black and white or are watching a presentation via a projector also benefit from a high contrast ratio. Sufficient contrast ensures that the content is clearly recognisable, making it easier to absorb and process information.

How can I implement/check it?

If you find that your presentation does not match the default contrast ratio of black and white, you can either change the font colour or adjust the background colour to increase the contrast ratio in PowerPoint. Here is a simple guide on how to do this:

1. Select the text for which you want to increase the contrast.
2. Click on the "Start" tab in the menu bar at the top of the page.
3. Click on the "Font colour" button under "Font " and select a colour with a higher contrast to the background colour. For example, if the background colour is dark, select a light font colour to increase the contrast.

It is also important to note that PowerPoint contains some accessibility templates that have been specially developed for recipients with visual impairments. If you use one of these templates, the contrast ratio is automatically optimised.

To ensure that the contrast ratio between text and background is optimal, you can use online tools or downloadable programmes. These can automatically calculate the contrast ratio for you.

If in doubt, it is advisable to opt for a dark text (preferably black) and a light background (white), as the contrast ratio of at least 4.5:1 is always given here.