Natural and Artificial Light, and How We Perceive Color.

The 10^th Edition of the Illuminating Engineer Society Handbook states: “Light” is a reserved category to describe an area of electromagnetic radiation that stimulates the visual system. Light is a psychophysical quantity and is, fundamentally, a perception. There are different forms of electromagnetic radiation, such as radio waves, microwaves, ultraviolet rays, and X-rays. Each type of electromagnetic radiation classification is based on its unique wavelengths. For example, radio waves can be miles long, while gamma rays are smaller than atoms. Visual light waves fall in the middle of the electromagnetic spectrum.

In 1704, Isaac Newton systematically studied the properties of dispersed light, correctly theorizing that the light of a distinct color reflects differently. Isaac Newton was the first to note that light of a distinct color had different brightness values and varied in their power to evoke unique visual sensations. Simply said, visual light waves give us the ability to see, and when selected light waves reflect off an object, they give us the ability to see color.

White light is a combination of all the colors of the visual spectrum. The primary light colors are red, the longest wavelength; blue, the shortest; and green, right in the middle. By combining either of these primary colors, we can create yellow, cyan, and magenta; combining all three, we produce white light. Different combinations of the three primary colors can illustrate all other colors.

When using an optical prism and passing a white light source through the prism, you can see the colors separate due to the prism’s ability to split the white light wavelengths and see what we refer to as the color spectrum: red, orange, yellow, green blue, indigo, and violet.

What is sight & the perception of color?

The human eye and brain combine to translate white light into color. Our perception of color results from millions of sensors in the eye referred to as rods and cones. Newton noted that objects do not have color but reflect and absorb other colors. So, how do we perceive color? Light transmits through the lens to an area in the back of the eye called the retina. Millions of light receptors embody the retina; there are two types: rods and cones. When these receptors sense light, they send visual impulses to the brain. There are three types of cone receptors: sixty percent red, thirty percent green, and ten percent blue. Every color stimulates more than one cone. There are over six million cones in the human eye. Their combined response produces a unique signal for each color and millions of assorted colors. Combined with connecting nerve cells, these cells give the brain enough information to interpret and name colors. Rods sense intensity and can help vision under low-level illumination.

So, when white light reflects off a white object, all spectrum colors are reflected off the object; equally, the object is white. If all colors are assimilated equally, the object appears black, and why is it red? All colors are reflected except red.

The Importance of Color Psychology

Distinct colors have been known to affect mood and feeling. Research has looked at the psychology of color and how color can stimulate human emotions.

As a designer, understanding the psychological influence of colors is akin to wielding a powerful paintbrush. Our palette is not just for aesthetics; it is a strategic tool that communicates, evokes emotions, and drives actions. Let us delve into the fascinating world of color psychology and its impact on design! Color is the silent communicator.

Colors are more than what meets the eye. They speak a silent language that conveys emotions, triggers memories, and shapes perceptions. Consider how warm tones like yellows and oranges radiate cheerfulness and optimism while serene blues and greens evoke tranquility and trust. Each hue holds the potential to elicit a specific response, and harnessing this power is at the heart of effective lighting design.

Think of iconic brands – the red and white of Coca-Cola or the golden arches of McDonald’s. These color choices are not accidental; they are strategic. Brands utilize colors to carve out a distinctive identity, establish recognition, and forge an emotional connection with their audience. A well-chosen color scheme speaks volumes about a brand’s personality and leaves an indelible mark in consumers’ minds.

Practical Tips for Lighting Designers

Here are actionable tips when harnessing the power of color:

• Research and Context: Understand color meanings in different contexts and how they align with your design goals.
• Consistency and Cohesion: Maintain a consistent color palette to reinforce brand identity and create a harmonious visual experience when lighting retail, hospitality, or other entertainment venues.
• Accessibility Matters: Ensure your color choices consider accessibility, making your design inclusive and user-friendly.

Understanding color temperature and how it impacts lighting design

Color temperature or Kelvin temperature is quantified as “the temperature of an ideal blackbody radiator that radiates light of a color comparable to that of the light source.” A blackbody is an object that absorbs all radiation, which includes visible light, infrared light, and ultraviolet light. In layperson’s terms, color temperature describes the warmth or coolness of color characteristics of a white light source.

Color temperature, in practice, is only valid for light sources that fall in a color spectrum of reddish/orange (yellow-based) to white (blue-based). This is because this spectrum corresponds closely to the radiation of a black body, while purples and greens do not. This range of color can be best demonstrated when heating a black body radiator, which initially emits red light that graduates from orange to yellow, then from white to blue as the temperature increases.

The spectrum of color temperatures is then assigned numerical values, measured in degrees of Kelvin. These values now describe the color emitted from luminaires with dedicated or stand-alone lamps when working with lighting.

Color temperature has essential implications for lighting. Ambient lighting will require a much more distinct color temperature than a space dedicated to detailed tasks. For this reason, see the general guide below to explain which type of space requires which color temperature to help you better decide the correct color temperature for your application.

Kelvin color scale

2200K – 2700K – Warm White
This 2700K color temperature is commonly used in residential spaces, restaurants, and hotels because it is warm, cozy, and has an inviting glow. 2200K is like sunset or candlelight and can be used in fine dining establishments.

3000K – Soft White
A soft white temperature still provides warmth but more clarity for completing tasks. This color is often used in bathrooms, kitchen areas, fashion boutiques, and fine apparel.

3500K – Neutral White
A neutral white mimics natural “mid-day” light and is ideal for spaces that require alertness, such as office spaces and retail stores. This light is still warm, easy on the eyes, and promotes focused activities.

4100K – Cool White
When an environment requires more precision, a cool white light is ideal. This lighting temperature is used in professional garages and grocery stores, which need crisp lighting for workers and customers to see details when working on a car and the colors of food as correctly as possible. This 4100K temperature is widely used in exterior applications because it mimics the light from a full moon.

5000K – Bright White
Locations that require very bright white lighting for ultimate clarity. These spaces include warehouses, sports stadiums, hospitals, ER rooms, and other industries with the brightest illumination needed to perform critical tasks correctly.

6500K – Daylight
This color temperature has a blue tone and mimics natural daylight from the sun. It is used for indoor farming, greenhouses, and other agricultural purposes.

As you can see, the color temperature scale is significant when choosing a lighting source. Every location and environment requires different lighting tones to best suit the activity in those spaces, and the wrong Kelvin color can affect the productivity of workers or the quality of work. To decide the color temperature you need, consider the tasks that will be performed in that space or the kind of feeling you want to convey.

What is the Color Rendering Index, or CRI?

CRI is a numeric scale established by the International Commission on Illumination (CIE). The CIE has established procedures and standards to evaluate how well an artificial white light source produces quality light when illuminating an object compared to under natural sunlight. This scale is calibrated from one hundred to zero, one hundred being the highest. The CIE states that levels in the upper nineties are excellent, the lower nineties excellent, and the under eighty are poor. Today’s high-quality LEDs render exceptional levels of color across the full spectrum of visible light, resulting in brilliant and beautiful colors for the viewer.

CRI Scale

CRI 95 – 100
Exceptional color rendering. Colors emerge as very natural as if lit by natural sunlight. Understated fabrics come alive and focused, skin complexion looks more beautiful, artwork graphics are more appealing, food looks more appetizing, and textures and paint show their true colors. CRI 95-100 is used widely in graphic arts, high-end specialty boutiques, paint sample displays, design-driven luxury hotels, art galleries, and residential spaces where natural colors must look their best.

CRI 90 – 95
Extraordinary color rendering. All colors come forth and are easily recognizable. The CRI of ninety is the starting point for high-quality lighting. Your spaces and furnishing look vibrant, and all colors are fully saturated. Clients will express positive visual cues, yet they will have little knowledge that the high LED CRI illumination is responsible for this incredible atmosphere.

CRI 80 – 90
A well-approved range for color rendering is here, and most colors are visually acceptable. Lighting practitioners for most commercial spaces use this range. Visual objects will not appear as fully color-saturated as you wish.

CRI Below 80
CRI is below eighty, and to the viewer, the lighting quality here is observed to have poor color rendering. Under this illumination, objects and colors may look unsaturated, flat, and unrecognizable. It would be difficult to distinguish between similar hues, such as black and navy blue. Objects of value lose their luster, color, and lower visual perception.

Understanding Color for Effective Lighting Design

It is important to note that today’s illuminated environments require lighting practitioners who can make highly educated decisions when reviewing plans as they work to create impactful spaces for us to enjoy. Color rendering, color temperature, and illumination intensity levels will all be essential to the final product.

In residential spaces, lower color temperatures (warm) with good color rendering (CRI > 80) create a comfortable, inviting space. In commercial or industrial settings, higher color temperatures (cool) with a high CRI help boost productivity and ensure that tasks are performed accurately. In artistic and creative spaces, high CRI with a balanced color temperature (around 4000K) helps ensure that true colors are displayed accurately without distorting hues or tones.

Overall, both CRI and color temperature influence a space’s visual comfort, functionality, and aesthetic quality, making them essential considerations in lighting design.