WCAG deck 1 Flashcards
What is luminance?
Relative brightness of a color, normalized from 0 (black) to 1 (white). It helps distinguish dark from light areas, especially for people with visual impairments.
Why is luminance important for accessibility?
It enables color-blind users to differentiate between light and dark colors, ensures content readability, and helps those with reduced or impaired vision.
What cones in the human eye contribute to luminance?
Red and green cones contribute to luminance, while blue cones do not.
What are the WCAG minimum contrast ratios?
4.5:1 for small text and 3:1 for large text.
What are the WCAG font size definitions for large text?
Normal weight: 18pt (24px) or larger. Bold weight: 14pt (18.7px) or larger.
How does ambient light affect color perception?
Colors are perceived differently in bright vs dark environments. Developers can use the AmbientLightSensor API to adapt styles based on lighting conditions.
What is local adaptation?
Local adaptation is the phenomenon where colors look different depending on their surrounding context, even if the ambient lighting remains constant.
How does dark and light adaptation differ?
Dark adaptation (adjusting to low light) is slow, while light adaptation (adjusting to bright light) is quicker but can be uncomfortable.
Why is blue a special case in contrast?
Pure blue is low in luminance, and there are fewer blue cones in the eye, making it less readable. Blue should typically be the darker of two colors or mixed with green to improve contrast.
Why should red and blue not be placed adjacent to each other?
Red and blue placed next to each other can ‘shimmer’ due to how the human eye processes these colors at different locations on the retina.
What is the purpose of contrast ratio calculations?
Contrast ratio calculations ensure sufficient luminance difference between text and background, improving readability and accessibility.
What tools can check luminance and contrast?
Browser developer tools and online contrast checkers can verify contrast ratios and luminance.
What is saturation, and why does it matter?
Saturation is the intensity of a color. High saturation, especially with red, can cause accessibility issues like photosensitive seizures.
How can developers improve text readability in animations?
Use low contrast and avoid flashes exceeding three per second to prevent triggering seizures.
How does luminance contrast help color-blind users?
Luminance contrast enables users to differentiate elements by lightness and darkness, even if they cannot perceive color differences.
