L*a*b* is a useful summary of color under one illuminant and observer. Spectral data preserves the wavelength-by-wavelength response from which those coordinates were calculated. That richer record is one of the main reasons a spectrophotometer supports decisions that a simple tristimulus colorimeter cannot.
A spectrum and L*a*b* answer different questions
| Data | What it represents | Main limitation |
|---|---|---|
| L*a*b* | Three coordinates calculated for a selected illuminant, observer and reference white. | Different spectra can produce similar coordinates under one condition. |
| Spectral data | Reflectance or transmittance values across measured wavelengths. | Still depends on compatible geometry, calibration and sample presentation. |
Because the spectrum is retained, software can apply recognised color-matching functions and illuminant distributions to calculate additional color values without physically remeasuring the sample—provided the original measurement is suitable for that calculation.
What spectral data enables
Multiple illuminants
Recalculate color under D65, D50, A or other supported illuminants and observers.
Metamerism analysis
Detect samples that match under one light but separate under another because their spectra differ.
Color indices
Calculate supported whiteness, yellowness, strength or other application metrics.
Process diagnosis
See where wavelength-specific changes occur instead of relying only on total ΔE.
Spectral targets also transfer more information between formulation, production and suppliers. Color-matching software can use them to guide pigment, dye or ink adjustments, while QC software can retain both the decision metric and its underlying evidence.
What a spectrum cannot solve by itself
A spectrum does not capture every aspect of appearance. Gloss, texture, sparkle, goniochromatic effects, translucency and fluorescence may require specified geometry or additional instruments. Reflectance and transmittance spectra are different datasets, and a calculation illuminant does not recreate a different physical UV excitation condition for fluorescent materials.
Compatible conditions still come first
Do not compare spectra from different geometries, SCI/SCE conditions, path lengths or sample presentations as if they were interchangeable. Richer data does not repair an undefined method.
The buying implication
If the task is limited to a stable pass/fail check under one fixed condition, a colorimeter may be adequate. If you need supplier communication, metamerism review, illuminant changes, color formulation, spectral troubleshooting or multiple indices, retaining spectral data provides substantially more flexibility. Confirm wavelength range, interval, optical geometry, transmission capability and software export before choosing an instrument.
Continue with spectrophotometer vs colorimeter, spectral reflectance, metamerism and instrument selection.
Last reviewed 21/09/2026 · Level: Fundamental
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