1.The concept of metamerism
Printing and dyeing industry often said that metamerism (known as jump light) as two shades under standard observer, when it under a specific light source (e.s CWF) these two shades are color matching however, when the light source changes the shades are no longer matched.
2. The reason of metamericsm
a. Light source: 
Light is an electromagnetic wave. The light causes the visual sensation of the human eyes that called visible light. The wavelength range at 400~700 nm, a single wavelength its capable of producing a specific color sensation that called Monochromatic light. 
However, the light produced by a general light source is made up of monochromeatic light of different wavelengths, which called polychromeatic light.
b. Color: 
The color is applied to the object by the light source through the absorption of an object, transmission and finally reflected from the object to the observer. Any object’s color has its specific reflectivity curve when it reflects the visible spectrum under the specific light source it will produce a spectral three stimulus to our standard observer. 
When the spectral reflectance and three spectra of two objects of different curves are equal, it considers these two objects have equal colors, once the light source changes due to each light source has different energy distribution the resulting spectral stimulus is no longer equal then it causes the jump light phenomenon.
3.Judgment Method
a.Perusal: Customers always use the light box to determine whether it’s acceptable or not. 
b.Color sensor evaluation: This method is more accurate because the equipment will return you the data.
4.How to avoid
a.Collect the color data: Collect the dyes and build up a data system, choose the most similar color based on customer’s standard sample. 
b.Experience: Checking the possible colors through the light box, choose the most possible and similar dyes to match.