Contrast impacts the readability of your content in print, on PowerPoint presentations, and on the web. Contrast is especially important for readers who are low vision or color blind. “Communicating with FINESSE” good practices include improving readability for those with visual impairments
Visual impairment
The Centers for Disease Control and Prevention describe visual impairment as the inability to see objects as clearly as a healthy person or to see as wide an area as the average person without moving the eyes or turning the head. Low visual acuity means vision between 20/70 and 20/400 or a visual field of 20 degrees or less.
Specific conditions include:
Photophobia – inability to look at light
Diplopia – double vision
Visual distortion or distortion of images
Visual perceptual difficulties or difficulties of perception
Color blindness
Color blindness (or color vision deficiency) is the inability or decreased ability to see certain colors or perceive color differences. Red–green color blindness is the most common form of color blindness, followed by blue–yellow color blindness and then total color blindness.
Vision Impairment and Color Vision Deficiency
Two rules normally apply when conveying information to people who are unable to see things as clearly as others.
Do not rely solely on color to convey meaning.
Ensure that there is adequate contrast between foreground and background colors.
Providing Adequate Contrast
Color contrast refers to a calculated ratio of the difference between foreground and background, including text, images, and videos. The goal is to ensure all content provides enough contrast so low-vision users can see and interact with it. A high contrast ratio will also help users outside or in a bright environment.
Web Content Accessibility Guidelines (WCAG) guidelines provide a standard for websites. Many web service providers, graphics software, and presentation tools use the WCAG Guidelines 2,0, Level AA, as the foundation for accessibility checking applications.
WCAG’s Color Contrast standards. According to these standards, the contrast requirements are:
4.5:1 for normal-sized text (standard links, body copy, etc.)
3:1 for large text. Large text (defined as bold font weight with an 18px or larger font size, or 24px or larger font size)
3:1 for user interface (UI) elements and graphics
The larger the font and wider the stroke, the more legible text will be at lower contrast.
How to Check
Common applications: Adobe, Google, Microsoft, and other companies that produce software tools include some form of accessibility checking, normally under the Review tab.
PowerPoint: Microsoft Accessibility can be used in conjunction with all PowerPoint presentations. Select Review > Check Accessibility to review and correct accessibility issues, including contrast.
Other Tools: The Center for Persons with Disabilities at Utah State University provides an excellent free tool (webaim.org/resources/contrastchecker/).
Applying It
Checking the contrast in your reports and presentations is not difficult. The dividends are huge when it comes to reaching people with visual impairments. The same good practices make all of your communication more effective. Are you communicating with FINESSE?
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