Color is one person's feeling, which is always with the individual subjective experience of the observer. The feeling of one seeing the color, others do not to know at all. So the color research is always full of mysterious imagination. At the same time, the colors make the world colorful. Visual arts, image display, printing and dyeing, textile and transmission, color printing, etc, is inseparable from the color researching. Therefore, the research on color and objective quantitative description is the object of many scientists.

In 1664, Newton dispersed the white sunlight into different color spectrums by a prism, which laid the physical basis of light color. In 1860 Maxwell matched from white to various color of light with different strength of red, yellow, and green 3 colors light, which laid the foundation of three- color colorimetric. On this basis, since 1931 the international lighting committee established and improves the colorimetric system of CIE. Now the CIE colorimetric system is widely used for expressing light color quantificationally. Colors can not appear without lighting as only under the light , the objects may display the colors and colors of light greatly affect people's psychology .Yang Gongxia, professor in Tongji University, has already made a wonderful description in the chapter 5 of his book” The visual and visual environment” about that in different light sources, the same object will display different colors. Such as the green leaves in green light appear bright green, while in red appear nearly black. Therefore, the source of light plays an important role for the objects. The ability of the light source which can fully display the color or not is called CRI of light source.

How shall we judge the CRI of LED bulbs simply? Without any testing equipment, we can only rely on intuition and eyes. You can take a lighting LED bulb in your palm. If the palm appears rosy color, which means the CRI is higher while appears cyan with low CRI. In addition, compare the different colors of a color object in different lights, and then compare the color in the sunlight .That will help you to judge the CRI of different lights.