Lighting Terms and Definitions

Helping You Choose the Best Lighting Solution

Commercial and architectural lighting is a spectacular combination of design, science, and innovative technology.

Using photometry, the science of measuring light in terms of perceived brightness, manufacturers can precisely explain how specific commercial or architectural lighting will perform.

Anyone purchasing commercial lighting or architectural fixtures must understand some extremely important terms and definitions, and be able to decipher specific diagrams.


Reading Photometrics and Specs in LED Lighting

Ambient Lighting – Lighting throughout an area that provides general illuminations.

Ballast – A device used with an electric-discharge lamp to obtain the necessary circuit conditions (wave form, voltage and current) for starting and operating.

Batwing Distribution – A symmetrical light distribution producing light angles to the right and left of the observer with comparatively little direct downward illumination as in the shape of a bat wing.

Beam Spread – 50% maximum candlepower.

Candela (cd) –  This is the term used to compare Luminous intensity. Candela is the unit of measure indicating the luminous intensity (candlepower) of a light source in a specific direction.

Candelas/meter² (cd/m²) – The quality of light that leaves a surface. This is measurement is what the eye can perceive which will offer more information about the quality and comfort of a design rather than its illuminance alone.

Center Beam Candle Power (CBCP) – CBCP is the maximum candlepower a lamp can achieve at nadir (angle between the vertical axis).

Color Temperature (Chromaticity) – The degree of warmth or coolness of a light source measured in degrees Kelvin (K).  The higher the degree K, the more blue, or cooler the lamp appears.  The lower the degree K, the more red or warmer the lamp appears.

Cutoff – Angle between the vertical axis (nadir) and the line of sight when the brightness of the source or its reflected image is no longer visible.

DLC – The DesignLights Consortium (DLC) promotes quality and energy efficient lighting for the commercial sector. When you buy a product that’s on DLC’s Qualified Products List (QPL), you’ve got yourself a superior lighting product.

Efficiency – The comparison between how much light is emitted from a luminaire. Efficiency% = Luminaire Lumens/Lamp Lumens

Footcandles (fv) – The measure of the quality of light that arrives on a surface. Luminaire intensity, direction of the surface, the distance from the luminaire to the surface, and the angle of incidence of the arriving light are all factors that affect illuminance. Undetectable to the human eye, this information is commonly included and used in specifying designs.

Lamp Information – Term used to identify the lamp designation and its initial lumen output.

Lumens (lm) – Luminous flux is measured in lumens (lm) which is the total amount of light produced by a source without taking direction into consideration.

Luminaire Spacing – Luminaire Spacing = SC x Height to Illuminated Plane

Luminance – Indicator of the brightness of an aperture. Spec sheets will sometimes include various viewing directions, the 0 direction being the direction where the light is aimed. Luminance is a primary indicator of the quality and comfort of a lighting system.

Spacing Criterion (SC) – A mathematical calculation of the maximum spacing allowed in order to achieve reasonably even illumination.

Test Number – Used to identify the specific lamp and luminaire combination being tested.

Unit LPW – Indicator of the total system efficiency.

LPW – Lamp Lumens x Luminaire Efficiency/Luminaire Watts

When looking over any manufacturer’s spec sheets, charts and graphics will play a vital role in describing fixture properties. From Candela diagrams to Downlight and Accent Charts, find explanations of each in this list.
The example spec sheet for the Lumenera V2 will give a better idea of how all these terms and diagrams come into play.

Accent – This graphic shows patterns of light from adjustable accent luminaires dependent on lamp type, wattage, lamp tilt and location of illuminated plane.

Beam Aiming – Diagrams allowing a designer to easily choose the right distance from a wall to locate a luminaire and find the center beam of the lamp where desired

Candelas – Diagrams that will graphically illustrate the light intensity at specific directions from nadir..

Cone of Light – Used for rapid lighting comparisons and calculations – cone of light is used to calculate initial footcandle levels for a single unit based on point calculation techniques.

Downlight – These charts show single-unit performance without considering inter-reflections from surfaces.

Wall Wash Data – There are two different kind of Wall Wash Data charts.

  1. Single-unique performance chart that plots the illuminance levels at one-foot increments along and down a wall.
  2. Multiple unit performance charts show the performance of the middle units computed from a four unit layout.


Outfitting a building with lighting is a crucial step in upgrading any industrial facility or architectural project. Understanding the terminology that goes along with choosing fixtures is essential.

Keeping this handy resource close by will make any purchasers life just a little bit easier.

At RLE Industries you will find a wide range of lighting fixtures for nearly any commercial or architectural lighting application imaginable. Click here to start browsing the variety of products or, call a trusted and experienced lighting professional at (888) 318-0500 for any additional questions about upgrading commercial or architectural lighting fixtures.


What Does DLC Approved Mean? Why Does DLC Certification Matter?

The DesignLight Consortium®

Energy Efficiency and Performance Standards

Searching for commercial lighting solutions can be challenging. Industry terms, certifications, and countless fixture options can make upgrading the lighting in any facility feel like a chore. A common term people might run across is “DLC Approved”. Understanding this common certification can pay off in a big way.

Lighting in an industrial facility, shopping mall, outdoor venue or parking lot is absolutely instrumental to improving productivity and safety. Without proper illumination, work won’t get done and safety could be compromised. If any owner of a commercial space is thinking about upgrading lighting, pushing the task off might not be an option. Many buyers are  left scratching their heads when it comes to navigating all the terms that come along with securing commercial lighting, and the explanations below could be exactly what they need to know.

What Is DLC Certification?

DLC certification is handled by The DesignLights Consortium® (DLC), a non-profit organization dedicated to accelerating the widespread use of high-performing commercial lighting solutions. The DLC established product quality specifications to promote high-quality, energy-efficient lighting solutions. They work with utilities and energy efficacy program members, manufacturers, lighting designers, and federal, state, and local entities.

The goal of the organization and certification is to create better energy efficiency programs by helping to identify and verify the highest-performing products and systems.

This voluntary certification initiative is set aside for LED technology and requires these lighting products to comply with specific standards in three areas:

  • Distribution
  • Color
  • Longevity

Only an accredited laboratory can test DLC lighting requirements, and these test results must be submitted directly to the DLC, by the manufacturer.

Rebate Programs with DLC Certification

All across the United States there are utilities that base rebate programs on DLC standards. DLC certified products include high bays, wall packs, lab lamps, roadway luminaires, retrofit-kits, decorative LEDs, and LED panels. Rebates depend on the location of the installation and can vary from place to place. Consulting with qualified professionals like those at RLE Industries is a perfect way to make sure any business is getting the most out of upgrading their lighting fixtures.

Businesses can benefit greatly by adding DLC Approved lighting solutions in a number of different ways. They can save energy, cut electricity costs, and take part in these rebates. Without knowing what to look for, choosing the best lighting options for any unique application will be a monumental challenge. Having a clear understanding of DLC certification, what it means, and why it matters can help purchasers make an informed decision.

If you have any questions about DLC Approved Lighting Options, or would like more info about RLE Industries’ Services, give us a call at 888-318-0500.