Billmeyer and Saltzman's Principles of Color Technology, 4th Edition

Chapter 4Numerical Color Specification: Colorimetry

We have learned that color is quite complex and can be described in many ways. We can describe physical properties that lead to color, such as colorant concentration or an object's spectral properties. We can describe physiological properties such as receptor responses and opponent signals. We can describe color perceptions using color names such as red and pink, or with color‐order systems. If a manufacturer and customer both have the same system, they can specify colors numerically and validate a material's color visually using the system's atlas. Physical standards and visual matching have been practiced, likely, for hundreds of years including today. For many applications, visual matching is inadequate because of a lack of control of illuminating and viewing geometries and variability in color vision. The solution to this problem is threefold and occurred during the early twentieth century. First, spectrophotometers were used to measure a sample's spectral‐reflectance factor. The spectrophotometers' geometries were standardized to include only two choices. Second, lighting was standardized to include only three choices. (Today, there are a large number of standardized illuminants.) Third, only two observers were standardized. The standard observers and lights were tables of data. By calculation, an object's color was defined numerically. This numerical system is the subject of this chapter.

A. COLOR MATCHING

One of the ...