Illuminant Metamerism:
Illuminant Metamerism is used to describe the fact that two lights with different proportions of energy at certain wavelengths may produce the same perception of colour . The word “METAMERIC” should not be used to describe objects which do not appear to match under any condition. For these objects, Fred Billmeyer suggests the word “PARAMERISM”.
Many metamerism indexes have been defined and are in use. One popular index of metamerism is a geometric average of color differences under two (or more) illuminants. MI2 = DE12 + DE22 . . .
A rule of thumb is the closer the curve shape or the more times two curves touch, the more conditions under which their object colors will match.
METAMERIC (adjective) : pertaining to objects whose color matches under one illumination condition or to one observer and not another.
METAMERISM (noun) : an attribute of a color match.
METAMER (noun) : one of a set of metameric objects
Different Types of Metamerism:
Metamerism is a problem that must be recognized and accounted for in industrial colour matching for different Industry as well as in textile industry. Different types of metamerism have been defined:
ILLUMINANT METAMERISM : It results from a change in illuminant
OBSERVER METAMERISM : Observer Metamerism is used to describe the fact that the same light may produce different perceptions of colour in different observers. It is results from a change in observer.
GEOMETRIC METAMERISM: Geometric Metamerism results from a change in viewing angle. It is sometimes used to describe the visual effect of specimens whose colour changes with direction of illumination or viewing. Velvet fabrics and pearlescent paints are just two examples of Geometric Metamerism materials.
Some have suggested the term INSTRUMENT METAMERISM to describe disagreement between instrumental and visual evaluations. This is usually a form of geometric metamerism.
Ref.:
- J.S. Setchell, in Colour Design (Second Edition), 2012
2. Photo by Quang Nguyen Vinh: https://www.pexels.com/photo/women-sewing-in-the-dark-14036021/