The criterion here is the color rendering property of a light source. It is called General Color Rendering Index, [Ra].

Color Rendering Index (CRI) is a quantitative measure of the ability of a light source to reproduce the color of different objects faithfully in comaprison with an ideal or natural light source.

The extent to which light is capable of making objects appear their true color is known as color rendering.

A lamp’s value on the Ra cale is showing its Color Rendering Index (CRI). The index from 0 to 100, for example, the incandescent has 100 Ra means the highest of CRI, if it is 0 Ra means the lowest of CRI.

The average 「shift」 in those eight colors samples is reported as Ra or CRI. In addition to eight color samples used by convention, some lighting manufacturers report an 「R9」 score, which indicates how well the light source renders a saturated deep red color.

Light source with high CRI, which are depend with color-critical functions. Although light sources having the same color temperature and same color appearance, it does not necessary means that the colored surface will look the same undert those. Those spectral wavelengths contained in the incident light that are reflected will determine the color impression that we obtain from the surface.