Once the lamp type and the “right” color temperature have been chosen, it is always recommended to use the highest CRI lamp available in that family. Electricity contributes to the highest percentage of expense associated with lighting and in order to make the best use of it, use the highest quality light source available.
There is no such thing as the absolute “true” color of any material: the perceived color is a function of the light it is viewed under. However, we can make a general statement: the higher the Color Rendering Index (CRI) of a light source (also denoted by Ra) the better – and more natural- colors appear under the light source.
The ability of any given light source to represent colors in objects is its Color Rendering Index or CRI. It is based on a relative measurement which will rate light sources on a scale of 0 to 100. The higher the CRI, the more natural the colors appear. Lamps with very good (70-80 CRI) and excellent (80+ CRI) color rendering properties are accepted as “high quality light” because objects and people will look more appealing and natural. As well, the light level itself will be perceived to be higher.
In measuring CRI, eight specific colors are compared against two reference sources: incandescent lighting is the reference for warm color lamps and natural daylight for cool color lamps. Both incandescent lamps and natural daylight are considered to have CRI’s of 100 even though, as we know, materials appear quite different when viewed under these two lights. These light sources are very different in color temperature although both have perfect CRI’s.
CRI is considered a useful measurement especially in settings where it is important for people or objects to appear as natural as possible. Examples include retail shops, restaurants, offices, hospitals, health clubs, paint shops, and print shops where high color rendering can reproduce natural hues and augment visual clarity.
|CRI Range||Rating||Typical Applications|
|80+||Excellent||Retail (displays, stores and shops)
|60 – 80||Good||Offices
High Bay Retail
Large Scale Exteriors (sports areas)
|< 60||Poor||Street Lighting