Color is one of the most fundamental perceptions of the human experience and flavors the world around us. Of course, our perception of color is completely dependent on light, which reflects off of physical surfaces and carries information about its color and texture to our eyes. But it’s not just the physical world that determines the colors we perceive. Light itself exists in a spectrum of observable color variants that shade and paint the world we see around us every day. Much thought has been put into understanding the psychology of color and how we might use the many colors of light to creatively manipulate our world. One of the best measurements we can take to facilitate this creative control is a Color Rendering Index or CRI.
The Color Rendering Index (CRI)
The Color Rendering Index (CRI) is a scale which describes the quality of light as a comparison to a standard light source. Typically the process compares eight standard color samples with a calibrated light source and then with the light source to be measured. Each of the eight color samples is graded from 0 to 100 based on how well it matches the calibrated light. The scoring is averaged and this is the CRI. A perfect match would be scored 100. Some monochromatic light sources emit strongly in one color band and these typically get a high CRI number on one or two color samples but score low in the remaining color samples. When averaged, the CRI is quite low – often under 20. Low-pressure sodium vapor lamps have a CRI near 0 , cool white fluorescent lamps have a CRI of 60, while incandescent lamps typically score at 100.
Since the CRI is a comparison against a standard, it’s important that an even comparison bemade. First, the color temperature of the sample and standard must be the same. Lower color temperatures contain more reds and yellows and this will skew the comparison if the calibrated light source is of a higher temperature color containing more blue. For this reason, the standard reference source between color temperatures of 2000 and 5000°K is a black body radiator such as an uncoated incandescent bulb. For color temperatures above 5000°K, sunlight at noon or a similar source is used.
While incandescent lamps have a CRI of 100, they are not the ideal light source in terms of color matching and rendering. This is mainly due to the incandescent color temperature being too weak in blue light, which can make it nearly impossible to distinguish shades of blue. Likewise, lamps with very high color temperatures such as 6000°K or higher lack the red spectrum and can make faces and warm colors seem washed out. The best light source for color rendering will bring together a daylight color temperature of 5000°K and a high CRI value above 75.
Unlike many lighting sources that are governed by their fundamental technology such as a glowing filament or a controlled electrical arc in a gas, LED lighting can be produced across a widely specified range of parameters. It is possible to blend color temperatures and CRI in an LED light fixture to achieve the optimal configuration. With this opportunity for different configurations comes the importance of working with a high quality lighting company so that the product you request is delivered exactly as required each and every time.
SpecGrade LED is a leader in high output lighting and advanced LED technology. We’re committed to outfitting your with the best possible lighting specifications for your particular application and we’ll work with your requirements to make sure you get the optimal solution.