The architecture of light: architectural lighting design concepts and techniques. A textbook of procedures and practices for the architect, interior designer and lighting designer pdfdrive com

Color Rendering Index:
This term describes the complexity or completeness of the spectral output of a light source.
Color Temperature:
This term describes the color that a light source appears to the eye due to an imbalanced spectral output.
COLOR RENDERING INDEX
Color rendering index is rather simple in principle and expression. The color rendering index, or CRI, of a light source is expressed as a number ranging from 0 to 100, where 100 is a spectral output that contains the entire visible spectrum and, therefore, renders all colors accurately. If a light source emits every wavelength in the visible spectrum, then the materials in an environment have the opportunity to reflect all of those wavelengths to the eye, and, thus, express all of the potential color in the environment.
The lower the CRI value, the fewer distinct wavelengths the source emits.
Therefore, fewer potential color expressions can be reflected from materials in the environment. When we go on to investigate various electrical light sources, we will see that color rendering capabilities (and corresponding CRI values) vary greatly from source to source. This variety is of huge significance to the designer. Since designers are responsible for making many critical material and color decisions, it is imperative that they are aware of the possible shortcomings of the light source under which they are making their decisions. Many a person has been shocked to find that two materials that look to be the same color under a specific electric light source look utterly different under daylight. Daylight represents a complete spectrum and, therefore, has a Color Rendering Index (CRI) of 100.
Incandescing sources like the common “light bulb” and halogen sources
are engineered to also emit the entire visible spectrum, so they also have a CRI of 100. A bad fluorescent source may have a CRI of 60. We will discuss the specific CRI values of various electric light sources in chapter eight when we investigate each source individually. Suffice it to say for general understanding that the following guidelines can get us through the system: