Spectrophotometry
Definition
Instrumental measurement of reflectance at each wavelength across the visible spectrum, producing a numerical colour profile. Results can be expressed in CIE Lab space or converted to Munsell notation, removing the observer-comparison step entirely.
- Field
- Forensic soil and colour analysis
- Measures
- Reflectance at each wavelength across the visible spectrum
- Output formats
- CIE Lab space, Munsell notation
- Advantage over visual comparison
- Removes the observer-comparison step
Common questions
Why is instrumental spectrophotometry preferred over comparing soil colour by eye against a Munsell chart?+
Visual matching depends on lighting conditions and the individual observer's colour perception, while a spectrophotometer produces a numerical value that is reproducible between examiners and instruments.
Can spectrophotometric data be converted back to a familiar Munsell notation for reporting?+
Yes, CIE Lab values can be mathematically converted to the nearest Munsell hue, value, and chroma, letting a lab report in the traditional notation while retaining the objectivity of the instrumental measurement.
Related terms
- Chroma
- The saturation or colourfulness of the hue, from 0 (neutral grey) outward in whole-number steps. Strongly weathered, iron-oxide-rich soils have high chroma;...
- Hue
- The dominant wavelength family of a colour, expressed as a position on the Munsell colour wheel. Soil hues run from 10R (red)...
- Inter-Observer Variability
- The tendency of different trained examiners to assign slightly different Munsell codes to the same sample. Research has shown this can span...
- Munsell Soil Colour Chart
- A physical book of matt colour chips arranged by hue, value, and chroma, published by X-Rite/Munsell Color. The analyst holds a chip...
- Value
- The lightness dimension of the Munsell system, scaled from 0 (theoretical black) to 10 (theoretical white). High-organic soils tend to have low...