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Quality of Finished Surfaces
Color and gloss have characteristics that may be separated and measured.
These measurements depend on the physical surface under inspection.
The viewed color of an object depends upon the visual characteristics of the viewer
and is a subjective measurement of a surface. Spectrophotometers can eliminate the
difficulties associated with color inspection. This type of instrument yields three
measurements of color: hue, saturation, and lightness.
- Hue - the component of color that corresponds to the spectral colors (red, orange, yellow, green, blue and violet).
- Saturation - measures the purity of the hue.
- Lightness - associated with the luminous intensity, usually the light-reflecting or transmitting properties of the object. The value ranges from white to black.
Color Scales
CIE Tristimulus Values, XYZ
XYZ was the first numerical scale offered to quantify color. All other color scales are derived from X, Y, and Z values.
CIE Chromaticity Coordinates, Yxy
XYZ was the first numerical scale offered to quantify color. All other color scales are derived from X, Y, and Z values.
Opponent Color Scales, Hunter Lab and CIELAB
The opponent color scales are the most popular because they are the easiest to interpret.
By looking at the numbers you can imagine the color. In some instruments, L, a and b values
are assigned.
- L or L* designates the lightness of the sample, where 100 represents white and zero represents black
- a or a* indicates redness when positive or greenness when negative
- b or b* indicates yellowness when positive or blueness when negative
For example: The corresponding CIELAB values for school bus yellow are:
| L* = 69.7 |
a* = 12.7 |
b* = 60.5 |
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