Setting Tolerances for Color Control 11

An example showing the ∆E for the L*a*b* color system. Photo courtesy of BYK-Gardner.

An example showing the ∆E for the L*a*b* color system.
Photo courtesy of BYK-Gardner.

A well-known, if extremely rough, convention in the world of color measurement says that in CIEL*a*b* or CIEL*C*h space, a dE* value of less than one indicates that two colors are visually indistinguishable to the human eye. The reality is far more complex than this. The limits of visual perception actually differ depending upon which portion of color space is being discussed.

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Understanding CIE Illuminants and Observers 12

A standard illuminant and observer are required in order to obtain color readings. Photo courtesy of BYK-Gardner.

A standard illuminant and observer are required in order to obtain color readings.
Photo courtesy of BYK-Gardner.

Color instruments and software packages all contain references to CIE standard illuminants and observers. What do these terms mean and how are they used in practical color evaluations? The CIE (from the French Commission Internationale de L’Eclairage), or International Commission on Illumination, is the worldwide authority on how we see and measure color. BYK-Gardner uses many of these standards in its instruments and available software packages. This paper will give some easy to understand explanations of these standards and how they should be used.

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