Not all white light is the same.
We know natural light can make an interior feel more spacious, but it can also make colors look better. Of course, natural light is not always available, so we turn to artificial light, which brings a whole host of considerations to the table, among them: energy use, brightness, and color.
In past blogs we’ve looked at some of the ways lighting can create ambiance or a productive work environment—looking more at the impact of the color temperature of the light source, which relates to the appearance of the light itself: does it feel cool or warm? This month, however, we are turning our gaze to another important consideration: how the light makes us perceive color. In order for the human eye to see the color of an object, that color must be present in both the object and the light that falls on it.
Color rendering refers to how accurately an artificial light source reveals the color of an object compared to how that color appears when illuminated by a natural light source. Rather than looking at the color of the light produced, we are going to look at the colors a light source helps us perceive, along with the importance of considering color rendering in architectural lighting design.
What is color rendering?
The International Commission on Illumination defines color rendering as the “effect of an illuminant on the color appearance of objects by conscious or subconscious comparison with their color appearance under a reference illuminant.” Said reference illuminant is typically the sun, with the goal of color rendering under artificial light being that colors will appear the same as they would under natural light.
Historically, the industry standard metric has been the Color Rendering Index (CRI), developed in 1974. A CRI score is given based on an artificial light source’s ability to most accurately reveal the colors of a subject with respect to sunlight. Rather than an indicator of brightness, the CRI indicates the percentage of the visible color spectrum that the sun would reveal of the same color, telling us how sharp those colors would appear. A light source with a high CRI will create a sense of vibrancy in the space. Conversely, low CRI will result in a washed-out, drab appearance.
Color rendering vs. color temperature
While not unrelated concepts, color rendering and temperature are distinct entities. Corrected Color Temperature (CCT) describes the appearance of light. Color temperature indicates the color output of a light source, measured in Kelvin degrees (as opposed to the actual temperature of a bulb's output). It refers to the temperature to which one would have to heat a black body in order to make it glow with the same color.
CCT tells us whether the light source produces a warmer yellowish glow, a neutral white tone, or more of a cooler blue tinge. In fact, even though a yellow glow is described as warm, it's actually at the lower end of the CCT scale, around 2700 Kelvin degrees, while that cooler blue tone is much higher at 6500 Kelvin degrees.
Color temperature is associated with how we perceive a space in terms of mood. Cooler blue tones can have an energizing effect, while warmer tones create a cozy, relaxing environment.
Why is strong color rendering important?
Our first thoughts when it comes to color rendering probably go to aesthetics. Certainly, lighting that produces excellent color rendering will create a vibrant, stimulating environment, particularly useful in the hospitality industry. When a light source can render more saturated colors, everything—and everybody—looks better. Lighting that helps the colors of décor pop also helps skin tones glow. The value of color rendering goes beyond the beauty of a space, however, and becomes critical in a number of different areas:
A more vibrant, colorful appearance is about more than just looking pretty: in retail settings strong color rendering will enhance the perceived quality of the products, particularly when it comes to items like fresh produce. A light source that does not render the color red as strongly, for example, could make a red apple appear dull and less appetizing, leading to food waste as produce is left on the shelf because it does not look as fresh.
Industrial facilities, such as food processing plants, factories, or assembly lines need to be sure employees can safely and accurately perform precision tasks. In order to ensure quality of this work, workers need to be able to easily and comfortably identify and distinguish colors as they perform these repetitive tasks throughout the day.
In surgical settings, high quality color rendering becomes critical—sometimes even a matter of life and death—when it comes to ensuring clear visualization of tissue around wounds or incisions.
Visually demanding tasks from reading to painting to makeup application need excellent color rendering not just to ensure a beautiful end product, but also to help minimize eye fatigue during tasks that take a long time to complete.
Measuring color rendering
With the rise of solid state lighting, researchers and designers have noted that CRI is not a universally accurate metric, particularly when it comes to evaluating LEDs. Solid state lighting products with low CRI scores have been found to render colors strongly, while other products with high CRI scores do not quite get the job done. Alternative metrics have been in development, including the Color Quality Scale (CQS), which captures a wider spectrum of colors and can reflect the impact of one color rendering poorly while the average of the others is strong—a situation that often results in overall poor color rendering to the eye.
For more information on color rendition research and standards, this collection by the U.S. Department of Energy provides several helpful resources.
Whatever system is used to gauge the final score, one thing is certain: the importance of color rendering in artificial light. High quality color rendering can enhance ambience, help move products, boost productivity, and even play a critical role in the accuracy of precision work. A light source with a strong color spectrum can make a space more attractive, healthier, and safer.
At CharterSills, we believe that when lighting is designed correctly, it can add dimension to the simplest of spaces. Lighting can turn an ordinary space into a work of art. Whatever design challenges clients present, CharterSills responds with a solution that exceeds their expectations. Contact us today at (312) 759-5909 or by email at info@chartersills.com.