Next-Gen APCA Contrast Tool
Calculate modern WCAG 3.0 APCA Lc perceptual contrast scores with font size and weight legibility matrices.
For regular body paragraphs (400 weight)
For bold headlines (700 weight)
APCA models how the human visual cortex processes spatial frequencies. Unlike legacy algorithms, it accounts for dark mode glare reduction and sub-pixel edge sharpness.
Technical Specification & Mathematical Principles
APCA determines perceptual lightness Y via spectral power laws (exponent 2.4) with flare compensation.
Contrast is computed as L_c = (Y_bg^0.56 - Y_txt^0.57) * 1.14 for dark-on-light, or (Y_bg^0.65 - Y_txt^0.62) * 1.14 for light-on-dark, producing a continuous score from -108 to +106.
Frequently Asked Questions
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