Expressing colors through symbols and numerical values is more precise than words.
When describing colors verbally, people use various expressions. However, can one accurately convey a color to others through words?
In Japan, it is said that the rainbow has seven colors, but some countries in the world describes it as five colors, while others may identify twenty.
If there were a universally shared color notation system, perhaps we could convey colors with confidence...
Wavelength and Hue of Light
When expressing color, the Munsell Color System is widely used.
As shown in the diagram, the Munsell Color System is a cylindrical coordinate color space, with brightness on the vertical axis, hue on the outer periphery, and chroma radially extending from the center.
Three-dimensional Diagram of Hue, Value, and Chroma
(Compliant with JIS Z 8721 Standard ColorChart)
Three-dimensional Diagram
Three-dimensional Diagram of Hue, Value, andChroma
(Compliant with JIS Z 8721 Standard ColorChart)
Munsell Color System: What are hue, value, andchroma?
Hue
There are five basic hues, (H) Red (R), Yellown(Y), Green (G), Blue (B), Purple (P), and the intermediate hues, Yellow-Red (YR), Yellow-Green (GY), Blue-Green (BG), Blue-Purple (PB), and Red-Purple (RP). Each hue has a scale of 0 to 10.
Value
(V) Value represents the ideal black as 0 and the ideal white as 10 on a scale. It quantifies brightness, allowing for comparison of brightness regardless of the hue.
Chroma
(C) Chroma indicates the intensity of the puremcolor components within a hue. Starting from 0 for achromatic colors, as you mix in pure color components, the color becomes increasingly vivid. The upper limit of chroma varies based on hue and value.
The brightness (Value) and chroma (Chroma) of 5GY (according to JIS Z 8721 compliant standard color chart).
Conversion of Sensory Colors into MathematicalFormulas for Precise Representation
When the human eye receives stimuli, it processes them into three primary colors: red, green, and blue, transmitting the information to the brain, allowing us to perceive color. In industrial applications, the tristimulus values (X, Y, Z) shown in the color matching functions below are used to correspond to the stimulation of these three primary colors. To quantify colors as numerical values, these stimulus values serve as a foundation. Through mathematical conversions (referto conversion formulas), various colorimetric values are derived.
XYZ chromaticity diagram---CIE (International Commission on Illumination)
Color Vision and Tristimulus Values
Isochromatic Functions
Conversion Formula
It represents every color with numerical valuesand expresses the color differences in a natural way.
While tristimulus values are fundamental numerical representations of color stimuli, they alone make it challenging to grasp the actual distribution of colors. Therefore, compared to tristimulus values, it is necessary to use a scale that has nearly uniform perceptual steps for color representation.
This need is addressed by the CIE (International Commission on Illumination) 1976 L*a*b* color space and 1976 L*u*v*.
Comparing the Two Corn Kernels on the Left:Using Numeric Values for Precise Color Differences
When comparing the two corn kernels on theleft, you might employ various expressions such as color intensity, glossiness, and vibrancy. However, using such descriptive terms may leave uncertainties about conveying the complete picture of the color differences. To provide a more concrete representation of the color disparity, numerical values like ΔE*ab can be used, ensuring a precise communication of perceptual color differences.
L*a*b* Color Space Chromaticity Values*
L*a*b* Color Space Solid
Regarding ΔE*ab:
The color difference ΔEab, representing the straight-line distance between two perceptual colors in the Lab color space, isgiven by the following formula:
If we designate the first measured color as A, and the second measured color as A', a color difference (ΔE*ab) emerges from A to A'. In this case, the color difference is assessed as described above in terms of L*a*b*.
ΔE*ab represents the distance from point A to point A'. Therefore, a larger numerical value indicates a greater distance, meaning a more significant difference in color.
