Accessibility · Cluster
Perception
Contrast, motion, and sensory alternatives.
- 01 Computing Relative Luminance and Contrast Ratios from sRGB Values The linearisation step, the weighted sum behind relative luminance, and why the WCAG ratio adds a constant to both values before dividing them.
- 02 Which Boundary Counts for Non-Text Contrast and Focus Indicators How the 3:1 requirement applies to component edges, icons, and focus rings, why the measured pair is the two colors on either side of a boundary, and how state changes are evaluated separately.
- 03 Redundant Encoding: When Color Cannot Be the Only Signal Why hue collapses under monochrome rendering and common color vision deficiencies, and the concrete channels — shape, position, texture, text — that carry the same information in parallel.
- 04 Measuring Contrast When Text Sits on a Photograph A single foreground color over an image has a contrast ratio for every backdrop pixel; how to find the worst case, and what scrims, blur, and backdrop filters do to that distribution.
- 05 Perceptual Contrast Models and Why Weight and Polarity Change the Verdict WCAG 2 contrast is a ratio between two colors; newer models predict lightness difference from a background and scale it by text size and weight, which makes polarity and stroke thickness part of the result.
- 06 Forced Colors Mode and the System Color Keywords How forced colors replaces author colors with a user-chosen palette, which properties survive, and the design habits that break when backgrounds are overridden but borders are not.
- 07 How prefers-reduced-motion Reaches an Animation and What It Cannot Stop The media query reports a user setting, so authors must honour it in CSS and in script; which motion triggers vestibular symptoms, and why duration is the wrong knob to turn.
- 08 Cue Timing in Captions and the Problem of Describing What Is Not Said How WebVTT cues are placed in time and space, what reading-rate limits imply about line length, and why audio description has to fit into gaps that the mix does not leave.
- 09 Computing the Flash Threshold: Luminance Steps, Area, and the Red Flash Rule Photosensitive seizures depend on the size, luminance delta, and frequency of a flashing region; how the general and red flash thresholds are defined, and why a small bright animation is a different risk from a full-screen one.
- 10 Checking Contrast Against What Renders, Not What Is Declared Computed styles, compositing, canvas readback, and the sampling decisions that decide whether a measured ratio corresponds to anything a reader sees.