One of the most fascinating aspects of our body design is our ability to perceive color. Often we do not place enough importance on the role colors play in our daily lives. Starting from just remembering objects based on their colors to letting them control our moods, colors are more integrated in our lives than we give them credit.
And central to all of this is lighting.
Light quality determines if an object will look appealing, dull or oversaturated. Put in improper light and food won’t seem appetizing, indoor plants will look depressing and people, in general, will seem devoid of energy or jarring.
As all our perceptions of aesthetics stem from the way they appear in nature, even the quality of light is measured against natural lighting. This is known as color rendering index.
Color Rendering Index (CRI)
While there are many measuring systems in place, Color Rendering Index is the most widely accepted one, for sources below 5000K. CRI is the measure of how faithfully an artificial lighting system can reproduce the colors of an object when compared with the performance offered by natural lighting. CRI contains measures for R1-R8 values, which are pastel colors and R9-R15 which measure how well saturated colors appear (e.g. R9 is red, and R18 pink). CRI is also typically measured as CIE Ra in commercial lighting, where Ra is the average performance for R1 through R8. For a lighting system to perform as perfectly as daylight, CIE Ra should ideally be 100.
Though a respectable measure, CRI at times fails to give the full picture of good lighting. For instance, a light source with a CRI values of 85 is considered to be optimal. However, it can still have poor R9-R15 values, thereby dulling down saturated colors.
As lighting systems are evolving, so are the metrics employed to evaluate their performance. Color Quality Scale (CQS) is one such measure. With a 15-color measure that is more nuanced than the CRI’s R1-R15 scale, CQS takes contrast and observer preference into account. This means that pure fidelity is not always a winning factor in this scale – at times, its just how the observer wishes to see a particular object, even oversaturated at times.
Until CQS becomes a universally accepted standard, the CRI scale has to be taken into account, keeping in mind, the performance for both low saturation high saturation colors.
As per the WELL standards, a good lighting system (excluding emergency lights, special purpose lighting and decorative fixtures), must offer the following:
- Color Rendering Index Ra of 80 or higher
- Color Rendering Index R9 of 50 or higher
To know more about CRI and light performance, visit: https://www.arraystorm.com/well-lighting