---
id: "20260728-0236-verify-against-a-primary"
title: "Capture: CIELAB's perceptual-uniformity design intent and blue-hue shortfall, verified against the primary CIE technical report"
type: "capture"
status: "promoted"
promoted_to: ["30-notes/claim-cie-15-2004-recommends-cielab-for-perceptual-uniformity.md","30-notes/claim-cie-15-2004-blue-region-nonuniformity-motivates-ciede2000-rotation.md","30-notes/claim-ciede2000-blue-hue-rotation-localized-near-275-degrees.md","40-entities/entity-cie-international-commission-on-illumination.md","40-entities/entity-ciede2000.md"]
not_promoted: ["Design-intent and blue-hue-shortfall claims were NOT duplicated as fresh notes — retrieve-before-write found both already covered by existing seedlings ([[claim-cielab-designed-to-remedy-ciexyz-perceptual-nonuniformity]], [[claim-cielab-lacks-perceptual-uniformity-in-blue-hues]]); those two notes were updated in place (audit_status appended, status bumped to budding, unverified-claim flags lifted) instead, and the three genuinely new Tier-1-sourced angles (CIE's own design-intent wording, CIE's own blue-region mechanism, Sharma et al.'s independent ~275 degree figure) became the three new claim-notes above.","Further leads (CIE Publication 142-2001, Luo/Cui/Rigg 2001, CIE 15.2-1986, CIE 116-1995, Kuehni 2002, Luo/Cui/Rigg 2002, the three CIEDE2000 mathematical-discontinuity threads, the anomalous-h_ab purple-line edge case) are leads, not claims made in this capture — none were fetched or quoted this run, so none became notes. Left as future capture targets; flagged in the journal and seek-flags.md as a structural noticing (foundational primary still unread).","Entity candidate, Luo/Cui/Rigg (2001) paper — not promoted: not itself a person/concept/term per the entity-page spec, and not yet read directly (the capture explicitly flagged it unread). Revisit once actually fetched and quoted.","Entity candidate, CIE 15:2004 (the technical report itself) — not promoted: a specific document, not a person/concept/term the entity-page spec covers; it lives as provenance in the new claim-notes instead.","Entity candidates, Gaurav Sharma / Wencheng Wu / Edul N. Dalal (persons) — not promoted: real named co-authors of one paper cited here, but the capture itself flagged this as the vault's known over-catching-co-authors-relative-to-foundational-ancestors blind spot; no second claim-note or independent recurrence yet makes any of the three individually load-bearing enough for a hub.","Entity candidate, CIE Technical Committee 1-48 — not promoted: single mention, capture's own framing was speculative ('relevant if the vault ever wants to track...'); UNSURE per the entity-page test, so left unpromoted.","Entity candidates CIE (International Commission on Illumination) and CIEDE2000 — PROMOTED (see promoted_to list above): both recurring/load-bearing across five-plus existing claim-notes, both established concepts per the entity-page test."]
origin: "batch"
writer_model: "claude-sonnet-5"
date_created: "2026-07-28T00:00:00.000Z"
provenance: "batch run 2026-07-28 — researched via WebSearch and mcp__seek__extract_pdf against CIE 15:2004 (Internet Archive-hosted PDF, tls:verified) and Sharma/Wu/Dalal 2005 (author's own University of Rochester-hosted PDF, tls:verified); commissioned specifically to close the primary-source gap flagged in [[question-verify-cielab-perceptual-uniformity-and-blue-hue-nonuniformity]]"
derived_from: []
tags: ["color-science","cielab","colorimetry","perceptual-uniformity","ciede2000","cie","primary-source-verification"]
source_url: "https://ia802802.us.archive.org/23/items/gov.law.cie.15.2004/cie.15.2004.pdf"
source_author: "CIE Technical Committee 1-48 (Division 1, \"Colour and Vision\"), International Commission on Illumination"
source_date: 2004
source_tier: 1
---


**Bottom line up front:** Both halves of the topic question are now confirmed against a genuine Tier-1 primary source — CIE 15:2004, *Technical Report: Colorimetry*, 3rd edition (the CIE's own official technical report, prepared by CIE Technical Committee 1-48 and approved by the CIE Board of Administration), fetched as a full PDF from the Internet Archive's copy of the U.S. federal incorporation-by-reference deposit and read in full via `extract_pdf`. This closes the gap left open in [[question-verify-cielab-perceptual-uniformity-and-blue-hue-nonuniformity]], which had flagged both [[claim-cielab-designed-to-remedy-ciexyz-perceptual-nonuniformity]] and [[claim-cielab-lacks-perceptual-uniformity-in-blue-hues]] as resting on a single Tier-4 Wikipedia citation. A second Tier-1 source — Sharma, Wu & Dalal (2005), the CIEDE2000 implementation-notes paper, fetched from the University of Rochester's own hosting of the authors' paper — independently corroborates the blue-region mechanism with a specific hue-angle figure (~275°).

---

## Claim: CIE 15:2004 confirms CIELAB was recommended by the CIE explicitly to give a perceptually more uniform alternative to CIEXYZ

**Claim type:** definitional/historical (what CIELAB was *for*). **Sourcing floor:** Tier 3–4 acceptable; **Tier 1 achieved** — this is the CIE's own technical report stating its own recommendation.

Section 8.2, "CIE 1976 uniform colour spaces," opens: "Pending the development of an improved coordinate system, the use of one of the following coordinate systems is recommended whenever a three-dimensional spacing perceptually more nearly uniform than that provided by the XYZ system is desired." Section 8.2.1.1 then defines CIELAB itself as: "Three-dimensional, approximately uniform, colour space produced by plotting in rectangular coordinates, L*, a*, b*..."

This directly upgrades [[claim-cielab-designed-to-remedy-ciexyz-perceptual-nonuniformity]] from a Tier-4 Wikipedia paraphrase to the CIE's own primary wording: the space was recommended specifically because CIEXYZ's spacing is *not* perceptually uniform, and CIELAB is offered as a (self-described "approximately") uniform successor. Note the CIE's own qualifier "approximately uniform," appearing in the space's very definition — the CIE's technical report does not claim CIELAB achieves perfect uniformity, only that it is intended to approximate it better than CIEXYZ.

| Field | Value |
|---|---|
| source_url | https://ia802802.us.archive.org/23/items/gov.law.cie.15.2004/cie.15.2004.pdf |
| source_author | CIE Technical Committee 1-48, International Commission on Illumination |
| source_date | 2004 |
| source_venue | CIE 15:2004, *Technical Report: Colorimetry*, 3rd edition, Section 8.2 / 8.2.1.1, p.16–17 |
| source_tier | 1 |
| exact_quote | "Pending the development of an improved coordinate system, the use of one of the following coordinate systems is recommended whenever a three-dimensional spacing perceptually more nearly uniform than that provided by the XYZ system is desired." |
| exact_quote_2 | "Three-dimensional, approximately uniform, colour space produced by plotting in rectangular coordinates, L*, a*, b*..." |

---

## Claim: CIE 15:2004 documents CIELAB's residual non-uniformity in the blue region by name, as the specific motivation for the CIEDE2000 rotation term

**Claim type:** technical-mechanism (how the space actually behaves, and how the corrective formula addresses it). **Sourcing floor:** Tier 1–2 required. **Tier 1 achieved.**

Section 8.3.1, "CIEDE2000 total colour difference formula," states plainly that the correction exists because CIELAB is non-uniform: "The CIEDE2000 total colour difference formula corrects for the non-uniformity of the CIELAB colour space for small colour differences under reference conditions." It then identifies the blue region specifically as the site of a distinct geometric distortion: "Visual colour-difference perception data show an interaction between chroma difference and hue difference in the blue region that is observed as a tilt of the major axis of a colour-difference ellipsoid from the direction of constant hue angle. To account for this effect, a rotation function is applied to weighted hue and chroma differences." The report then gives the rotation term itself (R_T, built from a hue-rotation function Δθ) as Equations 8.43–8.45.

This is the primary-source confirmation that [[claim-cielab-lacks-perceptual-uniformity-in-blue-hues]] needed: not a Wikipedia paraphrase but the CIE's own technical report naming the blue region as the location of a specific, documented perceptual distortion (a hue/chroma-difference interaction tilting the color-difference ellipsoid off the constant-hue direction), addressed by a dedicated correction term in the CIE's own recommended formula.

| Field | Value |
|---|---|
| source_url | https://ia802802.us.archive.org/23/items/gov.law.cie.15.2004/cie.15.2004.pdf |
| source_author | CIE Technical Committee 1-48, International Commission on Illumination |
| source_date | 2004 |
| source_venue | CIE 15:2004, *Technical Report: Colorimetry*, 3rd edition, Section 8.3.1, p.20 |
| source_tier | 1 |
| exact_quote | "The CIEDE2000 total colour difference formula corrects for the non-uniformity of the CIELAB colour space for small colour differences under reference conditions." |
| exact_quote_2 | "Visual colour-difference perception data show an interaction between chroma difference and hue difference in the blue region that is observed as a tilt of the major axis of a colour-difference ellipsoid from the direction of constant hue angle. To account for this effect, a rotation function is applied to weighted hue and chroma differences." |

---

## Claim: An independent peer-reviewed CIEDE2000 paper corroborates that the blue-region correction is localized around a hue angle of ~275°

**Claim type:** quantitative (a specific hue-angle figure) + technical-mechanism. **Sourcing floor:** Tier 1–2 required. **Tier 1 achieved** — the authors' own paper, hosted on the corresponding author's University of Rochester page, published in *Color Research & Application*.

Sharma, Wu & Dalal, "The CIEDE2000 Color-Difference Formula: Implementation Notes, Supplementary Test Data, and Mathematical Observations," *Color Research & Application* 30(1):21–30 (2005), discusses the rotation term's impact directly: "Its impact is localized in the blue hue region (around 275°), outside of which Δθ and therefore the R_T term is rather small." The paper independently derives that the rotation term's discontinuity effects are "localized around a mean hue of 275°," consistent with the location the CIE 15:2004 report itself describes only qualitatively ("the blue region").

This gives the blue-hue claim a second, independent Tier-1 corroboration and supplies the specific numeric hue angle (~275°) that neither the CIE report's qualitative description nor the previously-cited Wikipedia sentence provided with sourcing this strong.

| Field | Value |
|---|---|
| source_url | https://hajim.rochester.edu/ece/sites/gsharma/papers/CIEDE2000CRNAFeb05.pdf |
| source_author | Gaurav Sharma, Wencheng Wu, Edul N. Dalal |
| source_date | 2005 (received 2004-01-28, accepted 2004-04-15) |
| source_venue | *Color Research & Application*, Vol. 30, No. 1, pp. 21–30 |
| source_tier | 1 |
| exact_quote | "Its impact is localized in the blue hue region (around 275°), outside of which Δθ and therefore the R_T term is rather small." |

---

## Further leads

- CIE Publication No. 142-2001, "Improvement to industrial colour-difference evaluation" (Vienna: Central Bureau of the CIE) — the actual CIEDE2000 standard document CIE 15:2004 cites (CIE, 2001a); not yet fetched directly, would be the single most-authoritative primary for the CIEDE2000 formula's own wording. (Cited in CIE 15:2004 references list.)
- Luo, M.R., Cui, G. & Rigg, B. (2001), "The development of the CIE 2000 colour-difference formula: CIEDE2000," *Color Research & Application* 26(5):340–350 — the original methodology paper the CIEDE2000 formula and the Sharma et al. implementation notes both build on; not fetched this run (see Entity candidates below — this is the paper whose earlier work the blue-region correction actually rests on).
- CIE Publication No. 15.2-1986 (2nd edition, predecessor to CIE 15:2004) and CIE Publication No. 116-1995, "Industrial colour difference evaluation" — cited in CIE 15:2004's reference list as intermediate steps between original 1976 CIELAB and CIEDE2000; not fetched.
- Kuehni, R.G. (2002), "CIEDE2000: milestone or final answer?" and Luo, Cui & Rigg (2002), "Further comments on CIEDE2000" — both *Color Research & Application* short pieces cited by Sharma et al. as addressing perceptual-uniformity/applicability questions the implementation-notes paper explicitly declined to cover ("does not in any way address psychophysical evaluation of the formula, attempt to improve its uniformity, or define its domain of applicability").
- Sharma, Wu & Dalal (2005) also documents three distinct mathematical *discontinuities* in the CIEDE2000 formula itself (mean-hue computation, hue-difference sign, and hue rollover at 360°) — a distinct, narrower technical thread from the blue-hue-uniformity question, worth its own capture if the CIEDE2000 cluster grows.
- CIE 15:2004 Section 8.2.3, Note 1 notes that "anomalous values of h_ab may be obtained" from the linear CIELAB formulae for transparent object colours of low luminance factor near the spectrum locus or purple line (McLaren, 1980) — a separate documented CIELAB edge case, not investigated further here.

---

## Central question: [RESOLVED]

Both parts of the topic question are confirmed against CIE 15:2004, the CIE's own primary technical report: (a) CIELAB was explicitly recommended by the CIE for perceptual uniformity, offered as a "three-dimensional spacing perceptually more nearly uniform" than CIEXYZ; and (b) the same report documents a specific, named non-uniformity in the blue region — a chroma/hue-difference interaction tilting the color-difference ellipsoid off the constant-hue direction — which the CIE's own CIEDE2000 correction (Section 8.3.1) was built to address. A second independent Tier-1 source (Sharma, Wu & Dalal 2005) corroborates the blue-region location with the specific figure of ~275° hue angle. This closes [[question-verify-cielab-perceptual-uniformity-and-blue-hue-nonuniformity]] and should be used to lift the `[unverified-claim]` flag on both [[claim-cielab-designed-to-remedy-ciexyz-perceptual-nonuniformity]] and [[claim-cielab-lacks-perceptual-uniformity-in-blue-hues]] at promotion.

## Entity candidates

- Luo, Cui & Rigg (2001), "The development of the CIE 2000 colour-difference formula: CIEDE2000" — person/paper — **flagged first, deliberately**: this is the FOUNDATIONAL paper the blue-region correction in CIE 15:2004 and the Sharma et al. implementation notes both rest on and measure themselves against; not yet read directly, and the vault's known blind spot is under-flagging exactly this kind of ancestor.
- CIE (International Commission on Illumination) — concept/organization — the standards body itself; already implicit throughout the vault's CIELAB cluster but never has its own entity page; worth one given how load-bearing "CIE recommends X" is across five existing claim-notes.
- CIE 15:2004 (*Technical Report: Colorimetry*, 3rd edition) — document/concept — the primary technical report itself; distinguishing it from CIE 15.2-1986 and CIE 142-2001 (the actual CIEDE2000 standard) matters because this capture cites the 2004 report's *summary* of CIEDE2000, not the 2001 standard directly.
- Gaurav Sharma, Wencheng Wu, Edul N. Dalal — persons — authors of the CIEDE2000 implementation-notes paper cited here; the paper's own co-authors, per the vault's noted blind-spot pattern of over-catching co-authors relative to foundational ancestors.
- CIEDE2000 — concept — already an unresolved wikilink referenced by three existing claim-notes in this cluster; this capture adds primary-source (not just secondary) grounding for its blue-region rotation term.
- CIE Technical Committee 1-48 (Division 1, "Colour and Vision") — concept/body — the specific committee (chaired by J.D. Schanda, per the report's own front matter) responsible for CIE 15:2004; relevant if the vault ever wants to track CIE technical-committee provenance as its own thread.

> [!note] Seek's commentary:
> The pleasant surprise here was how directly the CIE's own report answers both halves of the question in adjacent sections — Section 8.2 for the design intent, Section 8.3.1 for the blue-region shortfall, with the CIEDE2000 rotation term as the literal textual hinge between them. The "further leads" list is longer than usual because CIE 15:2004 turned out to be a hub document that cites its own predecessors and the actual CIEDE2000 standard by number; chasing CIE 142-2001 and Luo/Cui/Rigg (2001) directly would let a future capture quote the formula's origin in its own words rather than through the 2004 report's summary of it. — Seek