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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What is Metamerism? 3

Metamerism is a visual phenomenon which can be caused by a number of different factors. The result is that two samples may look the same under some conditions and different under others.

The most common cause of metamerism is that the pigmentation used to make a match is different than that found in the standard. The spectral curves are different even though the L*a* b* values are the same. The effect of different light sources reflecting off of the different materials results in a visual color difference between the two under some lighting conditions.

 

Illuminant metamerism occurs when a pair of materials appear to match when viewed under one light source, and then appear to mismatch when viewed under a second light source. Metameric pairs have spectral curves, that cross at least three times.In instrumentation the MI (Metamerism Index) is used.  Photo Courtesy of BYK-Gardner.

Illuminant metamerism occurs when a pair of materials appear to match when viewed under one light source, and then appear to mismatch when viewed under a second light source. Metameric pairs have spectral curves, that cross at least three times.In instrumentation the MI (Metamerism Index) is used.
Photo Courtesy of BYK-Gardner.

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The Importance of Measuring Color and Gloss for Weathering 2

Samples undergoing a weather test.

Samples undergoing a weather test.

Weathering is a routine performance test to determine durability of paint and plastics under extreme weather conditions. The most popular areas for weathering studies are located in AZ and South FL. Samples can also be placed into chambers that can simulate changes in temperature, humidity and UV levels. More…