CIELAB (1976) was built to fix CIEXYZ's perceptual non-uniformity — and still falls short of its own goal, especially in blues
The hop trigger was incidental: the seed paper's own novel contribution (carried as context-only in the vault) was applying the Kelley-Bryson-derived backprop to an "industrial color problem." That detail is a jumping-off point into a wholly separate lineage: industrial color measurement itself.
Core claims:
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CIELAB, the 1976 CIE color space, was created specifically to solve a usability problem with the earlier CIEXYZ space: "CIELAB was intended as a perceptually uniform space, where a given numerical change corresponds to a similar perceived change in color." (Wikipedia, "CIELAB color space," Tier 4 — definitional claim, acceptable per sourcing floor.)
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Despite that explicit design goal, CIELAB doesn't fully achieve it: "CIELAB is known to lack perceptual uniformity, particularly in the area of blue hues." Same source.
So the space built to replace a perceptually non-uniform predecessor is itself non-uniform in a specific, identified region of color space — a fifty-year-old open problem in colorimetry that later uniform-color-space proposals (CIELUV, CIEDE2000) have tried to patch rather than solve outright.
Why this was hop-worthy
A clean structural echo of the vault's favorite pattern (a formalism claims to supersede a flawed predecessor, but the successor has its own asterisk) — found by accident in a domain (industrial colorimetry) that has nothing to do with neural networks or optimal control.
Further leads
- Richard S. Hunter's 1948 Hunter Lab space predates CIELAB by decades — checked but scored more "adjacent" (0.635), likely because the priority/precursor framing itself pattern-matches vault content.
- CIEDE2000 color-difference formula — a later attempt to patch CIELAB's known non-uniformity.