Dominant Wavelength - Konica Minolta CHROMA METER CS-200 Instruction Manual

Dominant Wavelength

In the x, y chromaticity diagram shown below, the curve VS SR is the spectrum locus,
C
and point N is the white point.
Colors located in the region enclosed by the spectrum locus and the straight lines VN
and NR are referred to as spectral colors; colors located in the triangle NVR with the
white point N at the apex and the pure purple line VR as the base are referred to as non-
spectral colors.
Dominant wavelength (spectral colors)
For spectral colors, the dominant wavelength (generally symbolized as λd) is the wave-
length corresponding to the point on the spectrum locus (the curve VS SR) where a line
C
drawn from the white point through the chromaticity point obtained from the measured
values intersects the spectrum locus. In the example shown, for a measured chromaticity
point C, the dominant wavelength is the wavelength corresponding to point S, where the
extension of line NC from the white point N through chromaticity point C intersects the
spectrum locus.
Complementary wavelength (non-spectral colors)
For non-spectral colors, a line drawn from the white point through the chromaticity point
obtained from the measured values does not intersect the spectrum locus (the curve
VS SR), and instead intersects the pure purple line, which has no corresponding wave-
C
lengths. In such case, the complementary wavelength (generally symbolized as λc) is
used instead of the dominant wavelength. The complementary wavelength is determined
by extending the line in the opposite direction, from the chromaticity point through the
white point to the spectrum locus, and using the wavelength corresponding to the point
of intersection. In the example, chromaticity point C' is in the non-spectral region; the
complementary wavelength is the wavelength corresponding to point SC, where the line
extended from C' through white point N intersects the spectrum locus.
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