Demystifying Lumens Kelvins & Other Lighting Terms
Demystifying Lumens, Kelvins & Other Lighting Terms
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When it comes to understanding lighting terminology, it’s all too easy to feel left in the dark. Picking the right light bulb can be daunting, especially when there are dozens to choose from. Settling on the right one can enhance the ambiance and overall aesthetic of any room.
If you’re confused about which bulb is right for your needs, have no fear. We’ve compiled a comprehensive guide to common lighting terms with the help of Jeff Dross, Corporate Director of Education and Industry Trends at Kichler Lighting. Highly respected in his field, Dross has over 40 years of experience in the lighting industry and regularly conducts professional workshops all across the country.
From lumens and kelvins to correlated color temperatures, explore this guide to learn about the following:
- A brief history of light
- Breaking down key lighting terms
- What is white light?
- The importance of color temperature
- The Color Rendering Index (CRI)
- Color selection
- Lumens vs. Kelvins
- The Kruithof Curve study
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A Brief History of Light
The earliest artificial light converted nonvisible energy to visible forms of light using wood, oils, coal, and candles. These light sources produced color that was very warm and mimicked the natural beauty of an early sunrise and late sunset. Gaslight originated in the early 1800s and utilized open flames to achieve the same effect.
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From Edison to Modern Nostalgia (Hover to Toggle) -
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The first incandescent light was installed in 1880 and created both light and warmth by heating wire filaments via electricity.
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The first blue-toned artificial light gained ground in the 20th century, when arc discharge lighting was used in streetlamps, searchlights, and movie projectors until the end of World War II.
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By 1951, most light in the United States was created by the use of fluorescent bulbs. These lights were three times more efficient than traditional incandescent bulbs and lasted longer. Fluorescent lights became the preferred choice for American factories.
Breaking Down Key Lighting Terms
Behind every light design, innovation and breakthrough is science. In lighting, this is where the details really matter. Below we break down different lighting terms to help round out your understanding of light and what will work best in your home.
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What is White Light
Just like natural sunlight, white light is a uniform combination of red, blue, and green wavelengths. It contains light from the full visible electromagnetic spectrum. Because of this, white light has no wavelength of its own and instead contains all wavelengths, from 390 nanometers to 700 nanometers.
Since the color of visible light depends on its specific wavelength, we use two scales to characterize white light: correlated color temperature (CCT) and the color rendering index (CRI).
The Importance of Color Temperature
A light’s correlated color temperature (CCT) describes its visual appearance in terms of warmth or coolness. CCT is measured in Kelvins (K). The higher a light’s Kelvin rating, the cooler its overall light. The Kelvin scale ranges from 1000 K to 10,000 K, but most household fixtures fall somewhere between 2700 K (60W incandescent) and 3000 K (halogen).
Lower Kelvin ratings are soft, warm, and inviting, whereas higher Kelvin ratings are more practical for commercial locations or bright task lighting. Use the chart below to find the right color temperature for your styling preferences and needs:
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Pro Tip: Check out our Lamp Buying Guide for tips on choosing the right types of bulbs for table lamps, desk lamps, and floor lamps throughout your home.
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Color Rendering Index (CRI)
The color rendering index, or CRI, measures how a specific source of light influences and interprets an object’s color to the naked eye. The CRI scale ranges from 0 to 100 and indicates how accurate a light source is at rendering colors compared to that of a reference light source. The higher a light source’s CRI value, the better it is at distinguishing colors (and the closer it looks to natural sunlight). Incandescent and halogen bulbs render colors exceptionally well, while fluorescent bulbs have a more muted effect.
Pro Tip: CRI measurements of 80 to 90 are considered good, while CRIs of 90+ are considered excellent. -
Color Selection
The overall flexibility of LED light makes it easy to choose the color of white light that works best in a specific room. Not only can LED bulbs add color when and where it’s needed, but they also include color options when desired.
Contrasting colors fight each other when they’re mixed. For example, yellow light has the unique ability to dull cooler colors while simultaneously strengthening tones with similar warmth. Blue light, alternatively, enlivens dense, cool hues while weakening warm palettes.
Ideal for warm rooms, 2700K LEDs enhance beige neutrals, natural wood, earth tones, and sunny hues like gold, yellow, and orange. Alternatively, 3000K LEDs are a more neutral choice and work well with grey neutrals, blues, purples, greens, and classic black and white.
On the other hand, 4000K LEDs are typically best for commercial applications and can beautifully highlight crystal collections and sterling silver displays.
Familiarizing yourself with these common lighting terms can help you illuminate your home to perfection. Check out How to Shop for Energy-Efficient Light Bulbs for more lighting inspiration.
Lumens vs. Kelvins
Understanding the difference between lumens and kelvins can be tricky when picking out the perfect bulb for your light fixture. We’ll explore what these terms mean and how different values can impact your LED bulb’s performance.
Pro Tip: Check out our Light Bulb Buying Guide for more details on selecting the perfect bulb for your unique needs.
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First off, lumens refer to the brightness or intensity of a light bulb. For a long time, a light bulb’s overall brightness was measured strictly in terms of watts, but this has changed over the years. Keep in mind that wattage is a measurement of the energy consumed and has nothing to do with the quantity of light.
Both LED and traditional lights use lumens to determine how much light they will produce. LEDs can produce more lumens at lower watts.
Since LED bulbs naturally have lower watt ratings because they use less energy, it’s important to know the bulb’s lumens rating (lm) to better understand its brightness. In fact, when dealing with wattage (on anything other than incandescent), remember that these numbers are likely to change.
As a result, ignoring wattage in lieu of lumens is highly recommended as it’s the only real indicator of brightness. Keep in mind that a higher lumens value will emit a brighter light. -
"Today, 800 lumens of light can be delivered with as low as 8.5 watts. Last year, it was 11 watts and next year it could be down to 8 or 7.5 watts.” Dross said. “It can also depend on the manufacturer. Those using more advanced LED will consume less energy."
On the other hand, the Kelvin scale is used to measure the color temperature that a bulb will produce. A light’s Kelvin temperature for household fixtures will typically fall between 2000 K and 6500 K.
It’s important to choose a temperature that fits the need of a space. For example, Kelvin temperatures that range between 2000 K and 3000 K produce a warm, inviting light.
We’ve put together a lumens vs. kelvins chart to help you better understand how the two work to create a calming space. Keep in mind that there is no lumens-to-kelvins conversion. They are two physical units that are not directly related.
Pro Tip: Check out our Light Bulb Buying Guide for more details on selecting the perfect bulb for your unique needs.
Kruithof Curve
As lighting technology evolved, researchers began looking at human responses to specific color temperatures and levels of illumination. In 1941, Dutch physicist Arie Andries Kruithof collected psychological data on which colors and illuminance levels were most pleasing to human subjects.
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His study found that higher luminance levels are perceived to be more pleasing at higher color temperatures. On the other hand, lower luminance levels are perceived to be more pleasing at lower color temperatures. This region of visually pleasing light is known as the Kruithof curve.
In action, people enjoy being outside in the midday sun when it is bright and blue. In the evening time, people prefer dinner under a dim, reddish candlelit environment. Both of these examples prove what Kruithof discovered.
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