Object metamerism

There is a second type of metamerism that is important to discuss and that is observer metamerism. This is where two objects appear to one observer to be a... 

There are, necessarily, limitations to the above. Normally, the specular component of the reflected light is eliminated, and since the color matches are metameric, viewing conditions must be specified. Also, the greatest usefulness lies in the measurement of surface colors. The object should be opaque and nonfluorescent. The nature of the surface of tomato pur4e is far from ideal. Although many difficulties arise in borderline cases, and the result is dependent on the skill and color vision of the observer, the method has served a useful purpose. If however we examine the wording of the PMA specification, a sample shall contain as much or more red than that produced by spinning the specified Munsell discs. . . , it... 

Perception is easy—perhaps so easy we have a hard time finding words or formulas to describe the complicated appearance of objects. Many excellent scientific articles on the subject of metamerism appear each year in color literature (105) but even commonly accepted color tolerance models to which they refer are still under fire (106) (see Fig. 11). 

This scenario is a common occurrence in plastics and other industries. The reason is very simple. Two objects having the same color, when viewed under one type of illuminant (daylight), appear to match. The same two objects when viewed under different types of illuminants (incandescent) do not match. This phenomenon is known as metamerism. Metamerism is a phenomenon of change in the quality of color match of any pair of colors, as illumination or observer or both are changed. 

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