CIEDE2000

The CIE's 2001 color-difference formula, layered on top of CIELAB coordinates rather than replacing them — a metric patch for CIELAB's residual perceptual non-uniformity, most notably in the blue region. Its rotation term (R_T) exists specifically to correct a hue/chroma-difference interaction that tilts the color-difference ellipsoid away from constant hue angle near 275°. The vault's claim-notes had referenced CIEDE2000 as an unresolved wikilink across at least three notes before this promotion gave it a hub, and before a 2026-07-28 capture supplied primary-source grounding (CIE 15:2004 itself, plus the formula's own implementation-notes paper) for the mechanism.

• 2026-07-29: CIEDE2000 was one of three CIELAB-based color-difference formulas (with CMC and CIE94) that Urban, Rosen, Berns & Schleicher (2007) analyzed as non-Euclidean metric spaces with regions of nonzero Gaussian curvature obstructing isometric Euclidean embedding — a likely direct precedent for Ahrens et al. 2024's own "Euclidization" framing, evaluated against the CIELAB-based DE2000 formula specifically. Not yet quote-verified against Urban et al.'s own text. (claim-urban-2007-nonzero-gaussian-curvature-isometric-embedding-obstruction-unverified)

References

• claim-cielab-lacks-perceptual-uniformity-in-blue-hues · claim-cielab-only-approximately-uniform-fixed-by-noneuclidean-formulas · claim-cie-15-2004-blue-region-nonuniformity-motivates-ciede2000-rotation · claim-ciede2000-blue-hue-rotation-localized-near-275-degrees · observation-cielab-nonuniformity-bridges-gradient-geometry-not-sampling-artifact · claim-urban-2007-nonzero-gaussian-curvature-isometric-embedding-obstruction-unverified
• Related hubs: entity-cie-international-commission-on-illumination · entity-philipp-urban