Contrast Pattern Grade Estimator
Grade measured spatial RMS luminance contrast under caller independent bands and physical patch areas; differs from temporal scintillation, no laboratory cut grade or perceptual preference is inferred.
Description
Spatial RMS brightness contrast describes variation among visible patches.
Spatial RMS brightness contrast describes variation among visible patches. Physical patch area supplies the weighting and differs from temporal scintillation.1
Grade measured spatial RMS luminance contrast under caller independent bands and physical patch areas; differs from temporal scintillation, no laboratory cut grade or perceptual preference is inferred.
When to use Contrast Pattern Grade Estimator
Use this tool to grade measured spatial RMS luminance contrast under caller independent bands and physical patch areas; differs from temporal scintillation, no laboratory cut grade or perceptual preference is inferred.
Prepare the gemstone measurements, spectra or comparison data and any supplied calibration parameters. Check units, reference conditions and record alignment.
How to use Contrast Pattern Grade Estimator and understand its results
- Prepare the gemstone measurements, spectra or comparison data and any supplied calibration parameters. Check units, reference conditions and record alignment.
- Enter normalizedPatchLuminances, representedPatchAreas, callerContrastGradeLowerEdges using the field table and calculation rules, then run the tool.
- Read areaWeightedLuminanceContrast, callerContrastGradeCode. The explanation below defines the units, signs, ordering and any flags or placeholder values.
- If the tool reports an input issue, correct the values and run it again. Apply the stated assumptions when interpreting a successfully returned result.
| Input field | Meaning | Value type; see rules below | Requirement |
|---|---|---|---|
| normalizedPatchLuminances | Normalized patch luminances | list of number | Required |
| representedPatchAreas | Represented patch areas | list of number | Required |
| callerContrastGradeLowerEdges | Caller contrast grade lower edges | list of number | Required |
Pair normalized patch luminances in [0,1] with positive areas and require positive mean. Compute contrast and classify it with 2–128 increasing caller lower edges covering the result; equality starts the corresponding zero-based band.
Paired lists must be nonempty and have equal lengths.
contrast=sqrt(area-weighted population variance)/area-weighted mean luminance Units, indexing, boundary conditions and exceptional cases are defined in the calculation rules above.
| Output field | Meaning | Value type |
|---|---|---|
| areaWeightedLuminanceContrast | Area weighted luminance contrast | number |
| callerContrastGradeCode | Caller contrast grade code | number |
{
"input": {
"normalizedPatchLuminances": [
0.2,
0.8
],
"representedPatchAreas": [
1,
1
],
"callerContrastGradeLowerEdges": [
0,
0.3,
0.7
]
},
"output": {
"areaWeightedLuminanceContrast": 0.6000000000000001,
"callerContrastGradeCode": 1
}
}Limitations and assumptions
The bands are supplied, not laboratory cut grades or perceptual preferences.
Numeric inputs and returned numeric values must be finite; an unrepresentable returned value produces an error. Numeric lists are limited to 100,000 entries; the rules above may require smaller limits. Missing required fields, extra fields, wrong value types and violations of the calculation rules are input errors.
Alternative or Complementary methods
Use Scintillation Pattern Index: Integrate measured temporal brightness variation under piecewise-linear frames, retaining actual exposure; scalar scintillation proxy is not complete observer-dependent sparkle or commercial grade. For a complementary task, use Cut Grade Point Aggregator: Aggregate caller calibrated cut component assessments while separately retaining mandatory-component vetoes; high weighted score does not override failed local criteria or create a laboratory cut grade.
References
-
Contrast Pattern Grade Estimator — tool.io
Similar or alternative tools
- Scintillation Pattern Index
Integrate measured temporal brightness variation under piecewise-linear frames, retaining actual exposure; scalar scintillation proxy is not complete observer-dependent sparkle or commercial grade.
- Cut Grade Point Aggregator
Aggregate caller calibrated cut component assessments while separately retaining mandatory-component vetoes; high weighted score does not override failed local criteria or create a laboratory cut grade.