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Tolerancing Part 1: The History of Color Analysis

Posted February 21, 2018 by Tim Mouw

To control color, you need to be able to compare very small differences, determine their impact, and understand how to address that impact. But words alone can’t give us enough information to precisely describe colors, or the difference between them. In this three-part series we will look at the color science behind tolerancing – the color analysis that paved the way, the role of light, and the difference between a color space and a color model – so you can make the best tolerancing decisions for your business.

Munsell Color System

Albert Munsell was the first to establish an objective model of color communication. In fact, his empirical analysis of color organization from the late 1800s is the foundation of all modern color coordinate systems.

Munsell was a professor and an artist who noticed the colors he painted under sunlight didn’t match the colors he painted in the evening under lamplight. To help explain this phenomenon, he worked out a three-dimensional numerical system. The Munsell Color System, which we still use today, describes color using hue, value, and chroma.

Hue determines the color family. Munsell started with the main hues – red, blue, and yellow – then mixed them in various amounts to account for the subtle hue differences as each color blends together. He then assigned numbers to each one.

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Value describes the color’s darkness or lightness. While this terminology is rarely used today, the concept of lightness as a separate attribute of color remains central to all color coordinate methods – light blues and dark blues, light greens and dark greens, etc. To indicate the darkness or lightness of a color, Munsell assigned numbers ranging from 0-10 (10 is white and 0 is black).

Chroma describes the strength or saturation of a color. A color with high chroma will appear pure and strong. A color with low chroma will be muddy and gray.

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Munsell hand painted chips and arranged them to create a 3D model of color. The hues are located around the central axis. Value moves from light to dark down the axis, while chroma increases as it moves away from the axis.

Munsell Notation H V / C

He also bound them in the Munsell Book of Color as a structured, organized set of colors that (theoretically) contains all color possibilities. This page shows the different values and chroma of the 10P Purple Blue Family. The shades are clearly grouped by their major hue. As the color changes in lightness (value) and color strength (chroma) from lower left to upper right, the family (purple-blue) remains constant.

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Here is 10YR Yellow Red Family. When you compare these two families, you can see the purple family is “fatter” near the middle of the value scale. While this is partially due to our ability to see color, it is more is related to the availability of real, physical colorants.

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xrite-tolerancing-part-1-01With Munsell’s Notation H V / C ordering system, you can clearly identify and communicate colors. For example, this swatch (5R 4/12) has the following attributes: Hue (H): 5R Value (V): 4 Chroma (C): 12.

Munsell’s color system has been widely accepted and utilized. In fact, today’s color measurement software and instrumentation use hue, value, and lightness to calculate and compare the spectral values of color. He was ahead of his time and made a lasting contribution to the field of color analysis.

 

Want to learn more about tolerancing? You're in luck!