CIE colorimetry turns a light spectrum into a color by weighting it with standard human color-matching functions. Standard illuminants, such as D65 (daylight) and A (incandescent lamp, 2856 K), define the light.
In more detail
The CIE 1931 2° observer is the standard set of color-matching functions. A spectrum, an illuminant and the observer together give one reproducible color.
How we measure it
The Dichroscope and Polariscope use the CIE 1931 observer with D65, at 81 wavelengths from 380 to 780 nm. The Spectroscope lets you choose illuminant A or D65.
Related terms
- CIEDE2000 color difference: CIEDE2000 (ΔE00) is a standard formula for how different two colors look to a human observer. A larger number means a larger visible difference.
- Dichroscope: A dichroscope is a gem-testing instrument that shows a stone's two pleochroic colors side by side. In the calcite type, a calcite rhomb splits the light into two images of a small window.
- Spectroscope: A spectroscope is a gem-testing instrument that spreads light from a stone into a spectrum. Dark lines and bands show where the stone absorbs.
- Absorption spectrum: An absorption spectrum shows which wavelengths of light a stone absorbs. In a spectroscope, the absorbed parts of the spectrum look dark.