The angle of view and the illumination source are determining factors for metamerism.
Metamerism is the phenomenon that is generated when two color samples appear identical under certain circumstances and then, under other conditions, they turn out to be different . This is a term that is not part of the dictionary of the Royal Spanish Academy (RAE).
The word metamerism comes from the Greek metamerismos , which in turn is derived from meta , meaning "together" or "after," and meros , meaning "part" or "segment."
Causative factors
The two main factors causing metamerism are the viewing angle and the illumination source . Many times this phenomenon represents a complication when purchasing a paint , for example: people buy a certain tone according to how they perceive it in the sample and then, when applying the paint at home, they notice that it is different.
In order to avoid metamerism, companies that manufacture assembled or piece-based products use various processes and mechanisms, so that the result is homogeneous. The use of gloss meters , spectrophotometers , colorimeters and visual evaluation booths , in this framework, is frequent. It should be noted that metamerism can also be a problem for plastic artists due to the characteristics of the materials and supports used.
Luminance metamerism
The so-called illuminance metamerism occurs when the samples coincide under one type of light , but if they are viewed with another lighting, the color that is reflected is no longer the same. In other words, two objects that have a similar color appearance under a certain lighting may show differences in this appearance when the light is different. This is the most frequent optical phenomenon within this group.
This phenomenon is due to the fact that objects interact with light in different ways depending on their composition and structure . The way light is reflected, absorbed and transmitted varies depending on the physical properties of the materials. Different light sources emit different wavelengths and energy distributions, which affects how objects interact with that light and how we perceive their color.
Illuminance metamerism can have important implications in fields such as graphic design, textiles, printing, and color reproduction . For example, two colors that look the same on a computer screen may show noticeable differences when printed on paper due to variations in lighting and the reflective properties of the paper.
Geometric metamerism
Geometric metamerism , meanwhile, depends on the viewing angle. In this way, if the samples are seen from a particular point, they match, although from another position they no longer match. Another phenomenon of this group is field metamerism , associated with the changes that occur with distance.
Note that the objects or surfaces observed must have different geometric characteristics for this phenomenon to occur, which depends on the viewing conditions . Despite their differences in shape and structure, their visual appearance is similar or indistinguishable due to certain shared visual properties.
Two different objects can look similar if viewed from a certain angle.
In the context of color , geometric metamerism refers to the ability of two objects with different spectral reflectance characteristics to produce the same color stimulus in the human visual system. This occurs when the responses of color receptors in the human eye are similar for both objects, despite differences in their spectral properties.
Geometric metamerism can be used in applications such as color reproduction, calibration of display devices and printing , where it is sought to achieve a consistent visual appearance of colors despite differences in the physical properties of materials . It is important to note that this phenomenon only occurs under certain specific conditions: changes in lighting conditions, viewing geometry or observers can reveal real differences between objects that appeared to be metamers at first.