Delta E CMC Calculator

Compute asymmetric CMC l:c same-white CIELAB difference with caller positive lightness/chroma weights; reference/sample direction matters and l:c choice does not certify color acceptability.

Description

CMC l:c color difference weights a sample relative to a chosen reference.

CMC l:c color difference weights a sample relative to a chosen reference. Swapping reference and sample can change the result.^[1]

Enter two same-white Lab triples with L 0–100,a/b±200 and positive lightness/chroma weights≤100. Derive SL,SC,SH from reference lightness/chroma/hue and return asymmetric weighted difference; squared hue residual is floored at zero.

When to use Delta E CMC Calculator

Use Delta E CMC Calculator when you need to evaluate the supplied records under the calculation and evidence rules below. No universal acceptance threshold, spectral match or reference-white adaptation 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 Delta E CMC Calculator 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 referenceLab, sampleLab, lightnessWeight, chromaWeight using the field table and calculation rules, then run the tool.
Read cmcReferenceWeightedDifference. 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
referenceLab	Reference lab	list of number	Required
sampleLab	Sample lab	list of number	Required
lightnessWeight	Lightness weight	number	Required
chromaWeight	Chroma weight	number	Required

ΔE=sqrt((ΔL/(lSL))²+(ΔC/(cSC))²+ΔH²/SH²)

Units, indexing, boundary conditions and exceptional cases are defined in the calculation rules above.

Output field	Meaning	Value type
cmcReferenceWeightedDifference	Cmc reference weighted difference	number

json

{
  "input": {
    "referenceLab": [
      10,
      0,
      0
    ],
    "sampleLab": [
      11,
      0,
      0
    ],
    "lightnessWeight": 2,
    "chromaWeight": 1
  },
  "output": {
    "cmcReferenceWeightedDifference": 0.9784735812133072
  }
}

Limitations and assumptions

No universal acceptance threshold, spectral match or reference-white adaptation is supplied.

Numeric inputs, where present, must be finite. Follow the calculation-specific rules for overflow, underflow and exceptional cases. Numeric lists are limited to 10,000 entries; string lists to 128 strings of at most 128 characters each. The rules above may impose smaller limits. Missing required fields, extra fields, wrong value types and violations of the calculation rules are input errors.

Alternative or Complementary methods

Use Delta E CIE94 Calculator: CIE 94 weights color differences relative to a reference chroma. Graphics and textiles use different constants. For a complementary task, use Delta E CIE2000 Calculator: CIEDE2000 adjusts Lab color differences for lightness, chroma and hue interactions. Neutral chroma and hue wrapping require explicit handling.

References

Delta E CMC Calculator — tool.io

Similar or alternative tools

Delta E CIE94 Calculator
CIE 94 weights color differences relative to a reference chroma. Graphics and textiles use different constants.
Delta E CIE2000 Calculator
CIEDE2000 adjusts Lab color differences for lightness, chroma and hue interactions. Neutral chroma and hue wrapping require explicit handling.