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    Color Matters

    Color science for professional LED lighting

    A new look at the science (and art) behind professional lighting

     

    Color science serves as an underlying technical foundation for the entire lighting industry. It establishes a consistent way of thinking about light—how it is created, controlled, and delivered in real-world implementations. A core understanding of the science of color is critical to lighting professionals, who must be able to specify the right light—color, technology, luminaire, and more—clearly and accurately. Only then can they achieve their unique vision, whether designing lighting for a home or an iconic architectural gem.

    The impact of LED lighting on color science


    Our understanding of how color is perceived and measured has changed over time, based on new discoveries, new color models, and evolving light sources. As with any disruptive digital technology, the introduction and market dominance of LED lighting renders many of the old ways of thinking about color obsolete. It also introduces extraordinary new capabilities, exciting opportunities, and new applications that were unthinkable, unaffordable, or impossible just a decade ago.


    But the move to LED technology also creates confusion. Lighting professionals now have to deal with new underlying approaches to color that go beyond the familiar RGB—including RGBA, RGBW, and other multi-channel luminaires. They have to stay in sync with evolving standards. And they have to choose from a broad array of system components—including luminaires, controllers, and sensors.

    Read more about the impact of LEDs

    As a visionary that helped lead the LED lighting revolution, Color Kinetics has a unique perspective on color science and deep knowledge of all aspects of lighting. We created Color Matters to provide lighting professionals of all types with a brief, easy-to-read guide that delivers:

     

    • an overview of core color science concepts
    • an exploration of how color science is changing in the LED era
    • an overview of Color Kinetics technologies that maximize performance and consistency
    • general guidance for specific lighting scenarios

    Traditional Color Science

    How is color perceived and measured?

     

    Man-made light is created for humans to perceive, appreciate, and benefit from—at home, work, and in public space. How we interpret and understand color involves the human eye and brain, which translate light into color perception. Light receptors within our eyes transmit messages to the brain, which produces the traditional, familiar sensations of color.

    That's the simple description—the more detailed version is even more remarkable.

     

    Why is color so complicated?

     

    Color is not inherent in objects—
    our eyes only perceive color in reflected light.

    This fact reveals some of the core complications of color and light, since light will vary depending on the surface that reflects it. And our physical perception and interpretation of light varies from person to person. In short, perception of light and color are subjective, not absolute.

    How do we perceive color?

    Important (and truly amazing)
    facts about color perception.

    Color preference

    Why do we prefer certain lighting
    sources and colors?

    How is color measured?

    Some of the ways light is measured via scientific quantification.

    How is color perceived?

     

    A full exploration of the complicated (and truly amazing) biological origins of color perception is beyond the scope of this brief guide. But these facts are important to know:
     

    • Since people have different percentages of red, green, and blue cones, they may perceive color—and differentiate hue—slightly differently. Since color perception is, ultimately, a construct of the brain, the signals to the brain will vary, making it impossible to compare color images that different people see.
    • Rods and cones comprise the key types of photoreceptor cells in the retina of the eye. Rod cells function in less intense light. Critical to peripheral vision and night vision, rods are concentrated at the outer edges of the retina. There are more than 90 million rod cells in the human eye. Cone cells are responsible for color vision and function best in relatively bright light. There are about six to seven million cones, concentrated towards the macula of the eye.
    Rods cones
    • Cultural differences and personal preferences affect color perception.
    • Some people (8% male, 1% female) experience some form of color perception impairment.
    • Blue-heavy white light sources have a higher perceived brightness, if the lumen values are the same.
    • The reflectance of the object (e.g., a wall) also impacts color perception, since it affects the amount of light/color that actually reaches the eyes receptors.
    • A MacAdam ellipse is the term used to describe the point at which a color difference becomes just perceptible to the average person viewing in a laboratory setting.
    • At very low light levels, people cannot perceive any color—only black and white, a phenomenon known as scotopic vision (vision of the eye under low light conditions).
    • As proof of the power of light, color light has a significant effect on the human sleep/wake cycle.
    • Perception of light also changes as the eye ages, creating the need for light sources to change and adapt to accommodate aging, as well as personal preferences.
       

    And as if color wasn’t complicated enough for an average person viewing, consider color synesthesia, a condition where a person perceives letters or numbers as inherently colored. Or chromesthesia, where sounds can trigger the perception of color.

    Understanding the foundation

     

    It’s helpful for today’s lighting professionals to understand color perception, including the basic physiological details of how humans experience and understand color. We’ve highlighted some of them here, but there are many other, more detailed resources online. And a working knowledge the various methods of color measurement is also important, since these concepts are central to how light is characterized, quantified, and specified. CRI, CCT, and many more—these acronyms are part of the specialized vernacular of the lighting industry.

    Color preference

     

    Researchers have been exploring color preference to identify why people tend to prefer certain lighting sources and colors. As it turns out, many people tend to prefer lighting sources that had a larger gamut in the red area, causing slight oversaturation in the red range vs. daylight. Does this mean that lighting designers should specify more red? Ultimately, that’s a personal decision, one that weighs inherently subjective color preferences vs. staying realistic (e.g., close to daylight)—without distorting any individual color rendering.

    Color preference

    Understanding the foundation

     

    It’s helpful for today’s lighting professionals to understand color perception, including the basic physiological details of how humans experience and understand color. We’ve highlighted some of them here, but there are many other, more detailed resources online. And a working knowledge the various methods of color measurement is also important, since these concepts are central to how light is characterized, quantified, and specified. CRI, CCT, and many more—these acronyms are part of the specialized vernacular of the lighting industry.

    How is color measured?

     

    When the world was lit only by the sun, there was no real need to measure or quantify color. Light was simply light and colors were perceived by the world in a similar manner, though with the inherent variations created by perception and preference. With the advent of electric light sources (from incandescent to fluorescent to LED) came the need to quantify and accurately measure that light output1 — and to compare different light sources.

     

    Here are just some of the ways that light is measured via scientific quantification:
     

    • Lumen output: A traditional form of measurement
      The specification most commonly used for evaluating and comparing the performance of conventional lighting is lumen output. However, complete and accurate definitions of lumens and related terms are often technical and complex—and misunderstood. Lumen measurements should not be the only measurement considered when comparing light sources.
    • Correlated Color Temperature (CCT): A fundamental representation of white light
      The CIE2 1960 color space shows a range of color temperatures, measured in degrees K (Kelvin) along the black-body curve, from red to orange to yellow to white to blue. This progression is similar to the way a piece of iron changes color when heated in a blacksmith’s forge.

      CCT provides a basis for identifying the quality of light by assigning a color temperature to that light. This approach works well with incandescent bulbs, which use a filament that is heated until it emits light—so the temperature of the filament is also the color temperature of the light. However, CCT doesn’t take into account human biology and perception of light. It simply compares the color of heated tungsten to the color appearance of a light source—making it functionally obsolete in an LED context.
    • Color-Rendering Index (CRI): How well a light source renders colors
      Another key traditional measure of light and color is the color rendering index (again, devised by CIE), which measures the ability of a light source to reproduce the colors of standardized color samples—designated R1 to R8, with R9 (a saturated deep red color) often added. The color rendering score rates the faithfulness to the reference source—with a CRI of 100 being the highest fidelity compared to the reference source. For example, incandescent light sources have a CRI rating of 100. And color rendering under sunlight changes based on the time of day and weather conditions.

      As with other traditional color measurement methods, CRI presents problematic issues when characterizing LED sources. For example, CRI cannot effectively predict the color quality of white-light LEDs. And different sources with the same CRI value render colors very differently.

      For example, consider spectral power distribution. The three curves show wavelength content of three types of light—LED, fluorescent, and incandescent. While all three types of light create the same hue of white on a white wall, colored objects will render quite differently under each. CRI attempts to quantify source color rendering differences.
    Spectral curves
    1960 Color Space
    CRI
    1. Light output is the informal term for how much light a luminaire produces. The more technical term for data describing the visible light produced by a light source is photometrics.
    2. International Commission of Illumination, known as the CIE from its French title, the Commission Internatonale de I’Eclairage, an organization “devoted to worldwide cooperation and exchange of information on all matters relating to the science and art of light and lighting, color and vision, and image technology.”
    3. In fact, the black body is a theoretical object that absorbs all electromagnetic radiation that falls on it. Because it reflects no light, it appears black. And though no perfect black bodies exist, certain metals offer approximations.

     

    Understanding the foundation

     

    It’s helpful for today’s lighting professionals to understand color perception, including the basic physiological details of how humans experience and understand color. We’ve highlighted some of them here, but there are many other, more detailed resources online. And a working knowledge the various methods of color measurement is also important, since these concepts are central to how light is characterized, quantified, and specified. CRI, CCT, and many more—these acronyms are part of the specialized vernacular of the lighting industry.

    Color Science in the LED Era


    Traditional color science created a rational way for lighting designers and others to quantify the light output and describe specific color qualities of conventional incandescent lighting sources. CCT, CRI, and other measurements served as an accurate paradigm for defining light within that context. But as we’ve seen, the old standards are not ideal for the LED world. The accepted standards and their associated terminology will not go away (at least immediately) but will be supplemented by other, more precise ways of quantifying color—and differentiating between different light sources.

     

    Read more about standardizing LED evaluation


    As it often does, digital disruption (LED lighting) has inspired a parallel effort toward standardization. At some point in the future, our industry will adopt a standardized way of evaluating light source color rendition. Groundbreaking efforts, including Color Quality Scale (CQS), Gamut Area Index (GAI)—and now IES’s TM-30—can be seen as important steps toward the goal of standardization. But the day-to-day reality for today’s lighting professionals is that they have many alternatives available when choosing how to achieve their creative vision. Knowing these alternatives—and their particular strengths—is critical.

     

    Lighting design is all about choices.
     

    For lighting designers, the initial choice is between the three main varieties of light—white, color, or color-changing effects. This choice then leads to a second level of decisions—what type of light source to use to create that light. Before choosing a specific luminaire, form factor, or vendor, lighting professionals face a core decision about what type of light source will work best for their application.

    RGB, and beyond


    There are multiple approaches to color available now—which, ultimately, is good news for lighting professionals, who can tailor their choice to the specific needs of an application. In the past, designers had to use what was available, which meant RGB luminaires. But new options also trigger the need for careful decision making—backed by an understanding of the options.

    RGB

    RGB luminaires were the prevailing standard in color-changing installations for many years. Now luminaires combining red, green, and blue LEDs remain an option that allows a workable three-channel approach to creating color for a defined range of applications. It remains the default option for many luminaires, and gives lighting professionals a simple way to match legacy implementations—allowing for incremental addition vs. replacing all of the current luminaires.

    RBG chart

    RGBA

    Luminaires with red, green, blue, and amber LEDs expand the available range of colors to include warmer tones such as rich gold, yellow, and orange shades. The fourth channel enables creation of amber, a color that is impossible to achieve via color mixing of RGB channels alone. Whites will appear as the same color on a white surface, no matter what colors created it. But when viewing colored objects under the source, the differences become clear.

    RBG chart

    RGBW

    Adding a separate white LED creates better-quality whites compared to RGB, but lacks the ability to make amber tones. It also enables saturated reds, and a full range of pastels—as well as creation of white and diverse color light in the same luminaire.

    RBG chart

    IntelliHue

    Our advanced approach to color control and mixing produces an enhanced spectrum of precisely controllable light, including high-quality white, millions of saturated colors, and pastels all in the same precisely controllable luminaire. By combining carefully selected channels of LED light sources, IntelliHue enables high-quality dynamic color and white light from the same luminaire.

    RBG chart
    These approaches give lighting specifiers options that can match the specific demands of their application—and achieve their creative visions.

    Turning Science into Reality

    How to choose the right type of luminaire to achieve

    your creative vision

    The expanding range of assignments and implementations now possible with LED lighting creates challenges and opportunities to today’s lighting professionals. What type of lighting is right for a specific job? Will it meet the expectations for color, brightness, and consistency?
     

    Here are just a few real-world scenarios—indoor and outdoor—and our recommendations for the suggested type of Color Kinetics luminaire.

    Color Kinetics technology portfolio

    We continually explore your challenges, invest in research and development, and make the significant commitment required to develop and perfect breakthrough technologies. The result of decades of work, our unequalled portfolio of proprietary, quality-enhancing technologies helps you achieve the best possible results with our solutions. These technologies increase quality by ensuring sustainability, consistency, raising uniformity, providing precision control, and more.

    What matters in professional lighting?

     

    Optics are critically important. Our series of guides explores other key topics in professional lighting—Color Matters,  Quality Matters, Light Matters, and more. It’s part of our commitment to passing on our deep technical knowledge and decades of expertise to help you achieve your vision.

     

    No matter what Color Kinetics lighting solution you choose—or how you use it—you’ll get best-in-class technology and uncompromising quality. We bring expertise in LED selection, color science, delivered light, color consistency and control, data and power delivery, networking, remote monitoring—and all areas that matter to exceptional lighting.