Gamut Coverage / Color Space Notes Panel

Inspectable records

Ledger state

The current ledger marks this instrument verified clean within the source-bound verification corpus.

Area

Audio, Music, Photography & Color

Tranche

tranche-7

Evidence ID

t7-059

Ledger rows

1

No ledger note is attached.

Review findings

The lookup values and triangle-area arithmetic are standard and internally verified. Verdict is NEEDS_REVIEW because 'gamut coverage %' and the comparison denominator are not defined precisely, and the stated formula supports only an explicitly labeled CIE 1931 xy primary-triangle area ratio. Retain the honest educational/reference label and expose the metric name and reference denominator in the UI.

Formula and scope findings

• The CIE xy chromaticity triangle-area calculation is valid for comparing the geometric area enclosed by three RGB primaries, but it is not equivalent to perceptual gamut volume or actual display gamut coverage.
• The denominator for 'relative gamut coverage %' is unspecified. The test vectors assume the first listed/reference color space is the denominator, normally sRGB.
• A triangle-area ratio does not account for transfer function, luminance range, bit depth, achievable display primaries, black level, or volumetric/perceptual gamut differences.
• The color-space white points are listed as data needs but are not used by the stated triangle-area formula. If white-point adaptation or coverage relative to a reference white is intended, the algorithm must specify it.
• A chromaticity diagram overlay also requires a defined locus and coordinate convention, such as the CIE 1931 2-degree spectral locus in xy coordinates; that required plotting data is not explicitly specified.

Unit assumptions

• CIE x and y chromaticity coordinates are dimensionless.
• Triangle area is expressed in squared chromaticity-coordinate units, not physical area.
• Coverage percentages are calculated as 100 times the compared triangle area divided by the explicitly selected reference triangle area.
• All coordinates use the published CIE 1931 xy chromaticity convention.
• The published primary coordinates are treated as exact table values for these verification calculations; production code should retain the source precision.

Boundary hardening

BREAK_CLAIMED · SELF_FLAGGED

The boundary and undefined-selection cases require explicit validation, and the worked area calculation exposes a likely implementation hazard: inconsistent triangle-area arithmetic or chromaticity-coordinate tables can materially change reported coverage. The branch vector also shows that the correct area from the stated sRGB and Adobe RGB coordinates is 0.11205 and 0.15115, so any other values indicate a lookup or formula defect.

Errata and corrections

No applied erratum is attached to this unique-name record.

Inspectable example

4 review vectors are recorded. One source-bound sample is shown below.

{
  "inputs": {
    "color_spaces": [
      "Adobe RGB (1998)",
      "sRGB"
    ],
    "reference_color_space": "sRGB",
    "metric": "CIE 1931 xy primary-triangle area ratio"
  },
  "expected_outputs": {
    "Adobe_RGB_1998_triangle_area_xy2": 0.15115,
    "sRGB_triangle_area_xy2": 0.11205,
    "Adobe_RGB_1998_relative_to_sRGB_percent": 134.8951
  },
  "reference_data": {
    "Adobe_RGB_1998_primaries_xy": {
      "red": [
        0.64,
        0.33
      ],
      "green": [
        0.21,
        0.71
      ],
      "blue": [
        0.15,
        0.06
      ]
    },
    "Adobe_RGB_1998_source_convention": "Adobe RGB (1998) published color-space specification, widely tabulated standard value",
    "sRGB_primaries_xy": {
      "red": [
        0.64,
        0.33
      ],
      "green": [
        0.3,
        0.6
      ],
      "blue": [
        0.15,
        0.06
      ]
    },
    "sRGB_source_convention": "IEC 61966-2-1:1999 / ITU-R BT.709, widely tabulated standard value"
  },
  "working": "For Adobe RGB, A = 0.5 × |(0.64×0.71 + 0.21×0.06 + 0.15×0.33) − (0.33×0.21 + 0.71×0.15 + 0.06×0.64)| = 0.5 × |(0.4544 + 0.0126 + 0.0495) − (0.0693 + 0.1065 + 0.0384)| = 0.5 × |0.5165 − 0.2142| = 0.15115. For sRGB, A = 0.5 × |(0.64×0.60 + 0.30×0.06 + 0.15×0.33) − (0.33×0.30 + 0.60×0.15 + 0.06×0.64)| = 0.5 × |(0.384 + 0.018 + 0.0495) − (0.099 + 0.09 + 0.0384)| = 0.5 × |0.4515 − 0.2274| = 0.11205. Relative percentage = (0.15115 ÷ 0.11205) × 100 = 134.8951%."
}

Related workflows

No source-defined multi-instrument workflow membership is recorded.

Sources and evidence

These pointers bind the page to evidence. They do not grant authority or collapse verification into deployment.

• VERIFIED_LEDGER.json · VERIFIED_CLEAN
• evidence-tranche7/tranche7-results.json
• BOUNDARY_HAZARD_CATALOG.json