The standard sources term explaining in detail

As we all know, one cannot observe colors without observing light because colors do not exist without light. Natural light is the most ideal light source for color observation. But, restricted by time and place, people cannot engage in color matching under natural light all the time. Under most circumstances, they have to rely on artificial light source. When using artificial light source to observe colors, we often encounter the following phenomenon: two subjects appear to be identical in color under one artificial light source, but completely different under natural light (or another artificial light source). This phenomenon is known as metamerism of objects in physics.

To overcome the influence of metamerism on product quality during the process of color reproduction, International Standard Organization(ISO) and National Quality and Technology Monitoring Bureau demands that color reproduction and matching industry, such as advertising, graphic arts, printing and manufacturing of inkjet and toner,have to use standardized lighting condition for color observation. As a result, ISO especially came up with a regulation in 2000, i.e. ISO3664:2000, regulating in details the requirements for artificial spectrum used in standardized lighting condition, the brightness of the light source and the surrounding environment.