Blackbody Kelvin to xy Chromaticity Approx
Use bounded piecewise polynomial Planckian-locus xy approximation for 1667–25000 K; not spectral integration, measured lamp chromaticity, daylight locus or exact correlated color temperature.
Description
A bounded polynomial estimates Planckian-locus xy from blackbody temperature.
A bounded polynomial estimates Planckian-locus xy from blackbody temperature. A measured lamp need not follow that locus.1
Enter 1667–25000 Kelvin. Use x branches through/above 4000 K and y branches through 2222,4000 and above 4000 K. Return approximate xy.
When to use Blackbody Kelvin to xy Chromaticity Approx
Use Blackbody Kelvin to xy Chromaticity Approx when you need to evaluate the supplied records under the calculation and evidence rules below. No spectral integration, daylight locus, measured lamp color or exact CCT is supplied.
Prepare colors in the stated color space and scale. Use encoded RGB fractions, linear RGB, Lab, xy, byte values or ink percentages exactly as requested; supply caller tolerances and reference conditions.
How to use Blackbody Kelvin to xy Chromaticity Approx and understand its results
- Prepare colors in the stated color space and scale. Use encoded RGB fractions, linear RGB, Lab, xy, byte values or ink percentages exactly as requested; supply caller tolerances and reference conditions.
- Enter blackbodyTemperatureKelvin using the field table and calculation rules, then run the tool.
- Read approximateCieXy. 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 |
|---|---|---|---|
| blackbodyTemperatureKelvin | Blackbody temperature kelvin | number | Required |
Enter 1667–25000 Kelvin. Use x branches through/above 4000 K and y branches through 2222,4000 and above 4000 K. Return approximate xy.
x=piecewise reciprocal-temperature cubic; y=piecewise cubic in x Units, indexing, boundary conditions and exceptional cases are defined in the calculation rules above.
| Output field | Meaning | Value type |
|---|---|---|
| approximateCieXy | Approximate cie xy | list of number |
{
"input": {
"blackbodyTemperatureKelvin": 4000
},
"output": {
"approximateCieXy": [
0.3805283390625,
0.37673356643812816
]
}
}Limitations and assumptions
No spectral integration, daylight locus, measured lamp color or exact CCT is supplied.
Numeric inputs, where present, must be finite. Follow the calculation-specific rules for overflow, underflow and exceptional cases. Missing required fields, extra fields, wrong value types and violations of the calculation rules are input errors.
Alternative or Complementary methods
Use Planckian Track Duv Approximation: A local Planckian displacement projects measured chromaticity onto a normal at a chosen reference temperature. It is an approximation to Duv near that reference. For a complementary task, use CCT From xy Chromaticity Approx: McCamy approximate CCT uses an xy polynomial near a bounded domain. Not every chromaticity has a meaningful correlated temperature.
References
Similar or alternative tools
- Planckian Track Duv Approximation
A local Planckian displacement projects measured chromaticity onto a normal at a chosen reference temperature. It is an approximation to Duv near that reference.
- CCT From xy Chromaticity Approx
McCamy approximate CCT uses an xy polynomial near a bounded domain. Not every chromaticity has a meaningful correlated temperature.