Lighting Terminology

We will be the first to admit there is a lot of jargon in the lighting industry. It’s a technical field. However, we don’t want to elicit blank stares from any website visitors! The Q&A’s below will give you a great introduction to basic terminology. For more detailed definitions, check out our Lighting Glossary.

Q: What do the letters, LED, stand for?

A: Light Emitting Diode.

Q: I always say “light bulb” and you use the word “lamp.” Why is that?

A: Strickly speaking the words, “light bulb”, refer to the glass envelope of a light source while the word “lamp” is used in the lighting industry to refer to the entire light source – whether it is incandescent, fluorescent, or HID.

Q: What do you mean by color temperature?

A: The “color temperature” of a lamp refers to how reddish or bluish the lamp appears. If the lamp appears reddish, it has a lower color temperature (e.g., 2500K-3000K) and is considered to be “warm” in appearance. If the lamp appears to be bluish, it has a higher color temperature (e.g., 4000K-4500K) and is considered to be “cool” in appearance.

Q: What does “luminaire” mean?

A: The word, “luminaire”, refers to a light fixture; the two terms are synonymous.

Q: What does the rated life of a light bulb signify? 

A: The rated life of a lamp signifies the time at which 50% of a large quantity of these lamps will have burned out. That means that 50% of these lamps will burn out BEFORE the rated life and 50% will burn out AFTER the rated life. The rated life does NOT mean that every one of these lamps will last at least that long.

Q: What does the word “incandescent” mean?

A: The word, “incandescent”, means that the light source is heated up so hot that it begins to give off light as well as heat. That’s why incandescent lamps get hot and are so inefficient — most of the energy that goes into the lamp to create light really creates heat.

Q: What is “Color Rendering Index”?

A: The Color Rendering Index, or CRI, of a light source refers to how well it renders colors. If a lamp has a low color rendering index of say 50 it does not render colors very well. If, however, the lamp has a color rendering index of 80 – 95, its ability to render colors is thought to be very good to excellent. A CRI of 100 is considered to be perfect and is assigned to the sun itself.

Q: Why are A-line lamps being phased out?

A: The A-line incandescent lamp phase out is part of the Energy Independence and Security Act of 2007. Signed into law on December 19, 2007, this act was designed to reduce energy usage and greenhouse gas emissions.

Standard A-line lamps are incredibly inefficient. In fact, 90% of the power consumed by an incandescent bulb is given off as heat rather than light. Since lighting accounts for 22% of the total U.S. electricity usage, the phaseout stands to make a significant impact.

Energy-efficient alternatives, such as compact fluorescent lamps and LEDs, are viable replacements for the A-line lamps. Also, the act does not ban traditional incandescents altogether: It just calls for an efficiency improvement of about thirty percent. Currently, most incandescents using halogen technology are perfectly compliant with the new standards.

The federally-mandated phaseout will begin January 1, 2012. For more information, check out this brochure from the National Electrical Manufacturers Association. It explains the various options for replacing your A-line lamps and makes suggestions for each room of your home.