The Science of Light and Its Impact on Paint Color, Specification, and IEQ  

Halogen Lighting

First patented by General Electric in 1959, halogen lighting is considered a type of incandescent lighting, but with several advantages over the Edison bulb.

Halogen lighting is about 20 percent more efficient than conventional incandescents. More energy is released as light, and the lamps have a longer service life. The bulbs burn at a continuous level of brightness and have a life span of about 2,000-3,000 hours.

The spectral power distribution of halogen lamps is the closest of all light sources to daylight; it’s relatively balanced across the visible spectrum. Consequently, halogen is considered an ideal light source.

The color temperature of halogen is approximately 3000K, which is considered “warm” light, and it renders color at 100 percent. This relatively high color temperature enables good color rendition across a wide range of colors.

On the downside, halogen lamps have a high operating temperature, and while they are more efficient than other incandescents, they are far less efficient than LEDs. Hence, many countries have begun phasing them out, and in the United States they are rapidly being replaced by LEDs. Also, the light quality is not consistent. Though bright and white at maximum output, when dimmed, halogen light appears amber.

In addition to specific applications in homes and commercial buildings, such as task lighting, halogen lamps are also used for film projectors, vehicle headlights, floodlights, work lights, and in film production.

Fluorescent lighting

Though the technology was developed in the 1880s, the first fluorescent lamps weren’t available commercially until the 1930s. These lamps work by exciting a vapor inside a glass tube. As electricity passes between tungsten cathodes, the mercury vapor releases ultraviolet energy. A phosphor coating on the inside of the tube converts the UV light into visible light—a process called fluorescence.

Fluorescent lamps require a ballast, which controls the current to the lamp. The current must be modulated as the gas inside the tube ionizes and the resistance lowers; otherwise, the lamp would destroy itself.

From classrooms to grocery stores, fluorescent lighting is widespread in commercial and institutional buildings. Fluorescent lighting is seen in residential settings, particularly kitchens, and compact fluorescent bulbs, or CFLs, have replaced the traditional Edison bulb in many homes.

The light produced by early fluorescent lamps was cold and undesirable; however, phosphor technology has improved, resulting in more pleasing light with higher CRIs.

The spectral power distribution graph for fluorescent lighting reveals spikes at the red, green, and blue wavelengths, with little or no output at others. Colors appear cool. Blues and greens are enhanced, while reds and yellows are muted.

Fluorescents are available in a range of color temperatures, from warm whites (2700 K) to cool white (6500 K), and they have CRIs in the 80-plus range. They have a life span of about 8,000-10,000 hours.

There are several types of fluorescent lamps. Linear, or tube lights, remain popular for their energy efficiency and their even, diffuse lighting.

Compact fluorescent lighting was designed specifically to replace incandescent bulbs. CFLs entered the market in 1979. The great advantages of CFLs over incandescents are their energy efficiency and long service life. CFLs use 75 percent less energy than incandescents, with a 23 to 27-watt CFL providing the same light output as a traditional 100-watt incandescent bulb.

Fluorescents have some disadvantages. One is the warm-up time required. CFLs require thirty seconds or longer to achieve full brightness.

Over the years, the U.S. Department of Energy has upgraded efficiency standards for fluorescent fixtures. A 2010 rule effectively phased out T12 fluorescent fixtures in favor of T8 and T5 systems, which are much more energy efficient.

More recently, the U.S. Department of Energy mandated that all “general service fluorescent lamps” manufactured after Jan. 26, 2018, meet increased efficacy standards, as measured by lumens per watt. This rule eliminated 32-watt T8 systems, which did not meet the standards, and encouraged the adoption of either 25W or 28W T8s or LED T8 replacements.

Photo courtesy of Benjamin Moore & Co.

 

Light-Emitting Diodes (LEDs)

LEDs are available in a wide range of color temperatures from 2700K to 7000K and offer CRIs of 80 or higher. Warm white LEDs are crisp and the colors are vivid; cool whites tend to emphasize greens, blues, and violets.

LEDs are extremely energy efficient. With a life span that ranges from 30,000 to 50,000 hours, a typical LED will last up to four times longer than a CFL or fluorescent and 25 times longer than an incandescent source. What’s more, the life span of LEDs is not effected by the number of times they are turned on and off. In the United States alone, LED technology is expected to contribute to approximately 40 percent lighting electricity savings by 2030.

Aside from their energy efficiency, LEDs hold several other advantages. When LED lamps are dimmed, the color temperature remains relatively consistent. Unlike CFLs or fluorescent tubes, which require a warm-up time, LEDs achieve full brightness instantly. LEDs also contain no mercury or UV radiation.

Photo courtesy of Benjamin Moore & Co.

 

Natural Light and Daylighting

Few can argue against the appeal of a room flooded with natural light. In fact, daylighting can promote energy efficiency and occupant well-being, so long as glare and unwanted solar gain are controlled.

Natural light can have a significant and usually positive impact on color, but it is dependent on the room orientation and angle of the light. Light in north-facing rooms tends to be diffuse and cool. Hence, strong colors show well in these rooms, while lighter colors tend to look subdued.

South-facing rooms receive the most light, which can be a problem if left uncontrolled. However, these rooms lend themselves to a range of colors, whether cool or warm.

East and west-facing rooms have particular challenges. Light changes the most in these spaces. East-facing rooms benefit from warm morning light, but colors cool off as the sun moves higher. Similarly, west-facing rooms enjoy warm late afternoon and evening light, but colors may appear dull earlier in the day. In general, warm colors work well for these spaces.

A History of Health and Well-Being Research

Former University of Michigan psychology professors Rachel and Steven Kaplan have done a multitude of studies on how light impacts the health and well-being of humans. In the 1989 study titled “The Experience of Nature: A Psychological Perspective,” Kaplan and Kaplan found that when human enter a new environment, they cognitively search for elements that match their memories. This is how humans interpret new spaces and it is the brain’s way of being able to settle in and find comfort. Those memory-matching qualities might include spaces that remind us of childhood or another familiar context that makes us feel safe, welcome, and even joyful. Lighting is an important aspect of that experience. Light can be used to highlight any elements that induce familiarity, such as color, texture, and the shape of the space itself. For example, the way a brick wall is lit could remind a person of their neighborhood cafe. A framed art piece lit in just the right way could transport a person back to their childhood home.

For this reason, light is more than just a visual effect. It creates image, shape, intensity, perception, and contrast, but it can also deeply affect how a person experiences the space. It can improve or disrupt our sleep. It can impact our mood in either negative or positive ways. Studies have shown that light has the power to decrease depression and increase cognitive performance in measurable ways.

Brightness, hue, and saturation can evoke a wide range of emotions. Blue/white light has shown to make people feel more energetic, but can disrupt sleep patters around bedtime. Red/amber light is the least likely to disrupt sleep because it increases the secretion of melatonin, leading to better sleep and better cognition for the following day.

Colors themselves have a variety of associations. Black in interior design can increase a sense of strength, authority, elegance, mystery, aggression, and other moods, depending on how it is lit and used. Green can be used to evoke a sense of nature, health, calm and an array of other feelings.

Another area in which light and color can impact health and well-being is with seasonal affective disorder (SAD). SAD is a mood disorder that causes symptoms of depression during certain times of year, especially winter. It is a disorder than can affect anyone, even those without a history of depression. Light therapy is a common treatment of the disorder and is used to mimic natural light during dark and dreary days. Lighting and its interaction with color has the potential to create better environments for those suffering from SAD.

CHARACTERISTICS OF PAINT

Just as the lighting source can have an impact on how a painted surface appears, so can the type of finish and the composition of the paint itself.

All paints include four main components: resins (or binders), colorants and pigments, solvents, and additives.

Resins and binders hold the pigment particles together and provide film integrity and adhesion. Colorants and pigments provide color and hiding. They also protect the underlying substrate, control gloss and sheen, and provide other performance attributes.

Solvents thin the coating for easy spreading and application and evaporate as the coating dries. Additives provide specific properties such as mildew resistance, viscosity, and foam control.

The balance and quality of these four ingredients impact the paint’s properties. And finally, the overall quality of the color can affect the psychology of an occupant, and result in health and wellness impacts.

Light Reflectance Value (LRV)

An important consideration when selecting paint is the paint’s light reflectance value, or LRV. This figure represents the total quantity of visible and usable light reflected by a surface at all wavelengths and in all directions. Put another way, LRV measures how much light a surface reflects and how much light it absorbs.

LRV is largely dependent on color. This quality is measured as a percentage from 0 to 100, where zero is absolute black and 100 percent is perfectly reflective white. In reality, the most absorbing black has an LRV of about 5 percent, and an extremely reflective white has an LRV of about 90 percent.

LRV has important implications for daylighting and energy use. Dark colors absorb more light and heat; consequently, spaces painted with darker colors may require more artificial light to light them. They may also require more cooling energy or less heating energy, depending on the building location, orientation, and other factors. If heat gain is a concern, a good rule of thumb is to choose colors with an LRV of 60 and higher.

Lighter colors reflect more light back into the room and absorb less heat. A color with a high LRV will contribute most to daylighting and can reduce reliance on artificial light sources. Naturally, whites have high LRV values, but colors in the yellow family can achieve LRVs of up to 80 percent or 90 percent. An important consideration is that yellow grows exponentially more intense the more area it covers.

Knowing the color’s LRV can help the designer ensure adequate illumination for tasks and general lighting. LRV can also help delineate spaces and highlight hazards by optimizing contrast. Designers can often find the LRV of a paint color on the opposite side of the fan deck or through the manufacturer’s website.

Importantly, LRV is an invaluable tool for creating successful lighting plans that optimize daylighting and reduce reliance on artificial lighting. Commercial spaces such as auditoriums, classrooms, banks, lobbies, museums, and restaurants have a suggested LRV of about 70 percent. Industrial spaces such as warehouses, manufacturing, and shipping facilities have a suggested LRV of 65 percent.

ASHRAE also recommends minimum reflectance values for interior ceilings, walls, and flooring for various building types. The ceiling is the most important light-reflecting surface; hence, the recommended reflectance values are high—80 percent or more. Reflectance values for walls should be at least 50 percent, and at least 20 percent for floors.

Photo courtesy of Benjamin Moore & Co.

 

Reflectance and Paint Sheen

The type of finish on the paint affects how light is reflected from a surface. This, in turn, impacts how light is distributed within a space—and ultimately, how we experience it.

Think about a glossy versus a matte finish. The glossy surface will have more variation, with highlights that appear white or nearly so, while the matte surface will have a more uniform color.

To understand why this is, it’s helpful to understand the two main types of reflection: specular and diffuse.

Specular reflection is the mirror-like reflection of light from a surface. Incoming light from a single direction reflects off the surface in a single outgoing direction. Satin, semi-gloss, and gloss sheens produce specular reflection.

Specular reflection creates highlights on glossy surfaces, especially those with texture and “topography,” like molding. While specular reflection tends to make surfaces more interesting, it can also induce glare, which can cause fatigue and eyestrain.

Diffuse reflection occurs when incoming light is reflected in many directions. Matte, flat, and eggshell paint sheens produce diffuse reflections.

Diffuse reflection makes surfaces appear matte and uniform. This type of effect tends to obscure surface defects and can help contain glare; however, it creates a more monotonous painted surface.

Photo courtesy of Benjamin Moore & Co.

 

Impact of Sheen on Color Perception

Because of the way light reacts to glossy surfaces, light colors can appear lighter, and dark colors can appear darker in glossy sheens. Intuitively, it makes sense that the highlights in a glossy finish can make the color appear lighter. With darker colors, there is a greater contrast between the lighter highlights and the rest of the surface where light is not reflected. The overall effect is for the color to appear darker.

• To summarize:
• Matte, Flat, Eggshell tend to produce a diffuse reflection
• Satin, Semi-Gloss, and Gloss will produce a specular reflection
• Darker colors may appear darker in higher sheens

Requesting a Drawdown

Sheen is a quality of paint that impacts not only its appearance and durability, but how colors are represented. Typically, color chips are produced using an eggshell finish; however, the same color can appear lighter or darker in a glossy finish. If a project calls for a glossy finish, it is advisable to sample the paint color in the desired sheen to ensure the color is right.

Design professionals can request drawdowns to get a good idea of what the paint will look like in a given space with a certain type of lighting. A drawdown is a sample of paint from the actual color and sheen specified for the job. Drawdown cards usually measure 8 x 11 inches and are made by placing a small amount of paint on a plastic card and spreading it using a metal bar. This method eliminates distracting brush strokes and ensures consistent coverage.

Metamerism

An important consideration when selecting paint is a phenomenon called metamerism. Metamerism occurs when two colors that look identical under one light source look different from each other under another.

Metamerism occurs because the spectral power distributions of these apparently identical colors are different. When two such colors are plotted on a graph showing relative reflectance across all wavelengths, the curves will overlap if they are non-metameric but they will cross or intersect at least three times if they are metameric.

Metameric matches, or pairs, are quite common, especially in near neutrals, grays, gray-blues, gray-greens, and mauve, and the differences can be surprisingly dramatic.

Metamerism typically occurs when matching two colors that are made of different materials—for instance, paint and fabric. This occurs because the paint is colored with pigments, while the fabric relies on dyes.

Recall that colors can be created using additive (light) mixing or subtractive (substance) mixing. Blending pigments is different than mixing inks for printed material or using light to create colors on a computer screen.

Evaluating Paint Color and Ensuring Consistency

Metamerism is a key reason to evaluate color chips under various lighting conditions, including natural daylight and different types of artificial light. Manufacturer color chips are typically produced using an eggshell finish, as this finish is less prone to glare and provides an accurate rendition of a color.

Professional paint retailers typically equip their stores with state-of-the-art lighting technology and light boxes that enable a customer to view paint chips under various lighting conditions.

To properly evaluate color, specular reflection must be eliminated. This is accomplished by viewing color at an angle—ideally, 45 degrees from horizontal. This angle ensures only diffuse reflection is seen. It also eliminates glare, which can distort color.

When color standards are viewed in the lab under specialized lighting in a light box, a stand is used to hold a drawdown on a 45-degree angle to improve color viewing accuracy.

A key point to remember is that color formulas are not the same across manufacturers. For example, one manufacturer may use more green in their formula while another may use more blue. The undertones in the colorant are impacted by the changing light source.

In addition to the range in color formulas, product composition varies from manufacturer to manufacturer. For example, some colorants are made from solvents, which are paint thinners; others are made with waterborne technology. Such resins improve durability and hide without contributing volatile organic compounds, or VOCs.

For these reasons, it is recommended that design professionals indicate on their specification or contractor instructions that product substitutions are unacceptable. This is the best way to ensure that the end result is exactly what the designer or architect intended.

There is more than one way to make the same color. Paint color prescriptions and colorants vary from manufacturer to manufacturer. Some use proprietary colorant systems, while others rely on third-party sources.

Recall that paints exhibit a mass tone, or dominant tone, and undertone. Examine two seemingly identical colors from two different manufacturers, and you may find that one adds more red, while the other adds more yellow. This difference only becomes apparent once the paint is applied and the light source illuminates the surface. The color temperature of the light source effects the undertones in the colorants and may cause a color shift.

Another factor that impacts the tinted color is the quality of the base paint, or the paint before it is tinted. Base paints vary; some are slightly gray or yellow, while others are white. The quality of the base paint also impacts the quantity and distribution of colorant that is used to create the tinted color.

SPECIFYING PAINT COLOR

This section will discuss the key factors to consider when specifying paint: Application, Light Source, LRV, and Sheen, and will instruct design professionals how to use paint chips to successfully select paint color. It will also discuss the importance of paint schedules and paint specifications and what each should include. This section will also discuss how specifications can be used to avoid color discrepancies.

As we have seen, artificial lighting sources vary in their ability to render color. It will be important to determine the color temperature and CRI of the light source. Is the CRI adequate for the application? Remember, a CRI of 80 or above is acceptable for most spaces. A CRI of 90 or above will provide excellent color rendering. In many cases, artificial lighting can be supplemented by daylighting. Many if not most colors show well in natural light; however, keep in mind that light conditions change throughout the day and through the seasons, and the color will often be illuminated exclusively by artificial light. Light sources with CCT values around 3000 K will better mimic natural light. Also, keep in mind that higher LRV will increase the amount of light reflected in the room, whether the light source is natural or artificial.

The choice of sheen can make colors appear lighter or darker, so be sure to request a drawdown in the exact color and sheen specified for the job. Remember that sheen tends to impact darker colors more dramatically, and that glossier sheens can cause glare.

LRV and sheen will in part be determined by the building type and function. An industrial or healthcare project will have different requirements for aesthetics, performance, and durability than a residential project.

Finally, the manufacturer’s paint formula will have an impact both on paint performance and on how the color is perceived in different lighting conditions.

Photo courtesy of Benjamin Moore & Co.

 

Paint Schedules and Specifications

During the design process, much time and effort are spent selecting lighting and color for a space. All too often, however, contractors allow product and color substitutions on the job, often with disappointing results.

Design professionals can use schedules and architectural specifications to ensure the correct products are applied on the right surfaces.

A schedule is a list of materials, fixtures, finishes, building components, or equipment in table form. Schedules can be found on construction drawings, or in the project manual. The purpose of schedules is to avoid cluttering a drawing with too much text, and to quickly clarify the size, quantities, location, finish, etc., of items.

A paint schedule provides an easy to understand materials list for all the paint finishes required for a job. It also helps the painters identify where each color should go. Paint schedules typically indicate a manufacturer, product name and number, a color name and number, and gloss or sheen.

Schedules are an important part of construction documentation. However, a specification is still required to control the quality of the supplied coatings and how they are to be applied. Division 01 defines if and how product substitutions are to be proposed, evaluated, and approved. This is particularly relevant to paint specifications, due to the practice of color matching.

The best way to completely avoid color discrepancies in critical installations is to use a proprietary spec to dictate the manufacturer’s name, product, and color name and number, with instructions not to substitute product and no color matching.

CONCLUSION

Selecting paint is more than just choosing an appealing color. How a given paint color will actually appear in a space depends on a host of factors, including the lighting type, reflectance, finish, and formulation of the paint itself. Specification can also have psychological and physical effects on occupants of a space. Design professionals can use their knowledge of light and color to select the perfect paint for the given application and can translate their selections into specifications and schedules that ensure the exact product is ultimately used on the job and—ultimately—provides design elements that lead to environmental quality and health and well-being for the occupant.