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Lighting Glossary of Terms

This glossary will help you understand some of the key terms that lighting designers use to describe aspects of lighting fixtures and light quality. Higher-grade lighting fixtures will list these specifications, enabling your lighting designer select the right lighting fixtures for the task. For more information, reach out to your lighting designer or home technology integrator. Visit the Home Technology Association's technology budget calculator to obtain installed cost estimates of high-quality architectural lighting and lighting control systems. 

Beam spread

Beam spread refers to the angle at which light is distributed or spread out from a light source. It determines the size of the area that will be illuminated by the light, affecting how concentrated or diffused the light appears. Beam spread is measured in degrees and can range from narrow spotlights focusing light tightly on a small area to wide floodlights covering a broad space. Choosing the right beam spread helps achieve the desired lighting effect, whether highlighting a piece of art with a focused beam or softly lighting a room with a wide, gentle spread.

Center Beam Candlepower (CBCP)

CBCP is a measure of the luminous intensity at the center of a directional light source. Unlike most omnidirectional light sources, such as table lamps, downlights emit light from a single point in a given direction. Depending on the beam angle, the CBCP could vary greatly, even among fixtures with the same delivered lumens. Lumens are measured as the total light emitted from a source at all angles from that source. For this reason, CBCP offers a more use case-specific metric for determining lights in a given space and determines the “horsepower” or “punch” of the light source. It is not uncommon that a fixture with lower lumens but higher CBCP can deliver a brighter “punch” of light farther away.

Color temperature

Color temperature is a way to describe the appearance of light from a bulb, whether it feels warm like a sunset, cool like midday sunlight, or somewhere in between. It's measured in Kelvin (K). Here are some examples to help you relate to different color temperatures:

  • Warm White (2,000K to 3,000K): This light is cozy and inviting, similar to the glow of a candle or a sunset. It creates a relaxed atmosphere, perfect for living rooms or bedrooms where you want to unwind.
  • Neutral White (3,000K to 4,500K): This is crisp and bright, like morning sunlight. It's a balanced choice that works well in kitchens and bathrooms, where clear visibility is needed for tasks.
  • Cool White to Daylight (4,500K to 6,500K): This light is vibrant and energizing, reminiscent of a bright day's sky. Ideal for workspaces or reading areas, it helps with focus and concentration.

Contractor-grade lighting

These are the least expensive, entry-level basic lighting fixtures commonly sold at DIY home improvement stores or electrical distributors. They are engineered to be inexpensive. They typically have much more glare, a lower CRI, light quality inconsistency, which can be noticeable in a space with multiple fixtures, inferior dimming quality, and the least attractive trims.

CRI (Color Rendering Index)

Think of CRI as a scale that measures how true to life the colors of your room look under a light source. A higher number on this scale means colors look more vibrant and natural, just like they would in natural daylight. The highest number is 100, which would equal the light quality of the sun. A more modern and detailed measurement system for lighting quality is TM-30, see the definition below.

Flangeless or "trimless" fixture

A flangeless lighting fixture blends seamlessly with your ceiling. With no visible metal edge (flange), it creates a sleek, clean look.

Full-color lighting

This type of fixture can be set to any color, not just different hues of white light, like with ‘warm dim’ and ‘tunable white’ fixtures. Through subtle shifts in color balance, certain colors in art pieces can be emphasized. These lighting fixtures can also create dramatic and ‘moody’ lighting.

HCL lighting

HCL lighting, or Human-Centric Lighting, is a concept that focuses on enhancing human well-being and performance through the strategic use of light. It's based on the idea that the right lighting can mimic natural light patterns, supporting our body's circadian rhythms (our natural sleep and wake cycles). By adjusting brightness, color temperatures, and timing, HCL aims to improve our mood, productivity, and overall health, aligning artificial lighting more closely with our biological needs. It's like bringing the best parts of sunlight indoors, tailored to support us throughout the day.

Lighting control system

A lighting control system makes controlling your home’s interior and exterior lighting vastly more convenient than using banks of lighting switches or dimmers. They help provide the right amount of light where and when needed, reduce wall clutter, allow preset lighting scenes at the push of a button, increase security, helps save energy, and add convenience. Lighting control systems are sometimes referred to as smart lighting. Learn 5 reasons you may want a lighting system by clicking here.

Lighting designer

A lighting designer is your guide to achieving the perfect lighting setup in your home. They're experts in how light affects spaces and moods, and they use this knowledge to plan and create lighting schemes that enhance your home's beauty, functionality, and atmosphere. They’ll work with you to determine which rooms are most important, where you spend your time, the activity occurring in each room, and how much daylight may enter the space. In a nutshell, they help you get the right light in the right place at the right color temperature, aimed in the right way with the right beam spread. Whether picking the right fixtures or creating the right ambiance, a lighting designer ensures your home shines in the best light possible.

Linear lighting

Linear lighting refers to long, narrow fixtures that provide a continuous strip of light. This type of lighting is perfect for highlighting specific areas like under kitchen cabinets, along hallways, cove lighting, or over workspaces, adding a sleek and stylish touch to any room.


This is a measure of how much light you get from a bulb; in other words, it tells you how bright the bulb is. Unlike watts, which tell you how much energy the bulb uses, lumens tell you how much light you can expect. While lumens tell you how much light comes out of the face of the fixture, CBCP (see definition above) determines the “punch” of the light source. It is not uncommon that a fixture with lower lumens, but a higher CBCP can deliver a brighter “punch” of light farther away.

Lux (also referred to as "foot-candles")

This term represents the amount of light that hits a surface. It's useful for understanding how much light is needed to adequately illuminate a workspace or room. Lux uses the metric system, and foot-candles uses the Imperial measurement system. Lux is 10 times foot-candles. If you have 10 foot-candles at a spot on the ground, then you have 100 lux at that spot.

Small aperture fixture

These small and discreet lighting fixtures maintain tiny openings in the ceiling, focusing light in a precise area without being noticeable. They’re perfect for creating a subtle, elegant look.


TM-30 is a more advanced light quality measurement than CRI, giving better insight into how lights make colors look in a home. Think of CRI as a basic grade for how natural the light is, while TM-30 gives a full report card, showing not just how true the colors look, but also how bright and vivid they appear. It’s a way to make sure everything in your home looks as real and colorful as possible. The TM-30 uses two main scales to evaluate lighting quality:

  1. Fidelity Index (Rf): This scale ranges from 0 to 100, where higher scores indicate better color accuracy. It measures how faithfully a light source reproduces colors compared to a reference source, similar to CRI but in more detail.
  2. Gamut Index (Rg): This scale also ranges from 0 to beyond 100, showing how vivid or saturated colors appear under the light source. Scores around 100 mean colors are represented very naturally, while scores higher or lower indicate more or less color saturation, respectively.


A light fixture’s “trim” is the frame around a light fixture that you can see on the ceiling. It’s not just for looks; it helps control the light direction and spread. In some cases, the trim works together with an inner reflector, and in some cases, they are one piece. Trims can come in different styles and finishes, allowing for a bit of decorative flair.

Tunable white

A tunable white fixture’s light output can be set at any point between ‘very warm’ to ‘very cool’ white lighting. These are popular for HCL (human-centric lighting) and circadian rhythm lighting solutions, where the home’s indoor lighting can automatically mimic the sun’s natural daylight color temperature, which naturally changes throughout the day. Also, you can adjust the color temperature to enhance fabrics, wood tones, and other building materials. Warmer color temperatures are often more complimentary to reds, yellows, oranges, woods…while cooler color temperatures are often complimentary to blues, greens, and purples.

Warm dim lighting

A light fixture that automatically lowers the color temperature and light output simultaneously, based on how dim the light is adjusted to via a dimmer. For example, when the lighting is at 100% brightness, the color temperature could be 3000K, and when set to a soft dim, it lowers to 1800K, which is much ‘warmer.’ This mimics the behavior of incandescent halogen lighting fixture sources of the past.