---
id: "20260709-1613-hop-cielab-color-space"
title: "CIELAB (1976) was built to fix CIEXYZ's perceptual non-uniformity — and still falls short of its own goal, especially in blues"
type: "capture"
status: "promoted"
origin: "hop-batch"
hook_rule: "novelty-v0-preamendment"
model: "claude-sonnet-5"
date_created: "2026-07-09T00:00:00.000Z"
date_promoted: "2026-07-09T00:00:00.000Z"
promoted_to: ["30-notes/claim-cielab-designed-to-remedy-ciexyz-perceptual-nonuniformity.md (core claim 1 — design intent; definitional, Tier 4 within floor; seedling)","30-notes/claim-cielab-lacks-perceptual-uniformity-in-blue-hues.md (core claim 2 — blue-hue shortcoming; flagged [unverified-claim], seedling)"]
questions_routed: ["50-questions/question-verify-cielab-perceptual-uniformity-and-blue-hue-nonuniformity.md (open — primary CIE/colorimetry verification for both claims)"]
not_promoted: ["Further lead: Hunter's 1948 Hunter Lab space predates CIELAB — labelled a lead, not asserted; scored 'adjacent' (0.635); no standalone claim to promote. Left as a seed.","Further lead: CIEDE2000 as a later patch on CIELAB's non-uniformity — referenced (dangling wikilink) inside both notes rather than promoted as its own claim; a standalone CIEDE2000 note can be written if the cluster grows."]
hop_chain: ["seed: claim-backprop-special-case-kelley-bryson-formula (Mizutani, Dreyfus & Nishio 2000 — MLP backprop as a special case of the Kelley-Bryson optimal-control gradient formula)","seed's incidental detail (paper's own contribution: 'hidden-node teaching on an industrial color problem') -> tangent scan of Kenichi Nishio (0.657), Arthur Bryson aerospace (0.623), industrial color-matching/hidden-node teaching (0.609), Henry Kelley rocket trajectory (0.601), IJCNN conference history (0.574), Mizutani hydrology work (0.572) -> chose CIE color-space history (max_cosine 0.533)"]
novelty_max_cosine: 0.59
tags: ["color-science","cielab","colorimetry","perceptual-uniformity","hop"]
source_url: "https://en.wikipedia.org/wiki/CIELAB_color_space"
source_author: "Wikipedia contributors"
source_date: "n.d. (accessed 2026-07-09)"
source_venue: "Wikipedia"
source_tier: 4
---


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:**

1. 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.)

2. 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.