1. Where can I find lighting terms and technical information?
Our lighting glossary can answer some of your questions about technical lighting terms (like "What's an amp?" and "How do fluorescent lamps produce light?")
2. How can I get lighting product catalogs and sell sheets?
The Literature Library contains downloadable PDFs, including the latest full-line catalog and product sell sheets with in depth product specifications.
3. How can I get a Specifying Light and Color brochure?
You can download this brochure from the Learn About Light section of our web site.
British Thermal Units (BTUs) are the measurement of heat output. One BTU is the heat that will raise the temperature of one pound of water by one degree Fahrenheit. It is approximately the amount of heat generated by burning one blue-tip kitchen match. There are approximately 3.4 BTUs per watt per hour. High bulb temperature usually does not affect the life of the lamp unless the temperature is extreme. The filament of an incandescent lamp operates at a very high temperature (nearly 4750 degrees Fahrenheit for a 200-watt standard lamp). An increase of a few hundred degrees in bulb temperature does not noticeably increase the filament temperature, and there is practically no effect on the lamp life or light output. Glass in most general service bulbs withstands 700 degrees Fahrenheit safely.
5. How can I find the surface temperature of a lamp?
GE does not publish the surface temperatures of our lamps because there are too many factors which can affect the measurement of the bulb wall temperature, such as:
- The ambient temperature of the room
- Whether or not the surrounding air is still or moving (from wind, a fan, air conditioning, etc.) and at what rate
- The specific characteristics of the recessed fixture, such as its baffling, reflection, insulation, and ventilation properties
For more information, contact your fixture manufacture directly. Fixture manufacturers are able specify the maximum wattage and bulb shape of the lamp which can be safely to utilized in your fixture.
6. What is color temperature, and how does it indicate to the color of the light output from a lamp?
Color temperature (or correlated color temperature, CCT) is a number indicating the degree of yellowness or blueness of a white light source. Measured in kelvins, CCT represents the temperature an incandescent object (like a filament) must reach to mimic the color of the lamp. Yellowish-white (warm) sources, like incandescent lamps, have lower color temperatures in the 2700K-3000K range; white and bluish-white (cool) sources, such as cool white (4100K) and natural daylight (6000K), have higher color temperatures. The higher the color temperature the whiter, or bluer, the light will be.
For more about color temperature, visit the Selecting the Best Color Lamp section of our site.
Efficacy is a term used to describe the efficiency of a lighting product. This is measured in LPW, or lumens per watt. To determine the efficacy of a lamp, divide the lumen output of the lamp by the watts consumed. For example, a 60-watt soft white has 840 lumens and has an efficacy of 14 LPW.
8. How is quality of light determined?
Quality of light is determined by the relationship between the color temperature of the light, and the color rendering index.
The color temperature indicates the appearance created by the light source. The higher the color temperature, the "cooler" the color.
Typically, color temperatures of 2000K -3000K create a warm (yellow) appearance; above 4000K are cool (blue) in appearance. Between 3000K and 4000K are considered intermediate and tend to be preferred.
Color rendering index (CRI) rates a light source's ability to render colors in a natural way, based on a scale from 0 to 100. In general, light sources with high CRI (80-100) will make people and things look better than those with lower CRIs.
For more, visit the Quality of Light section of our web site.
Since fluorescent lamps have such a long life compared to incandescent lamps, eventually the brightness (lumen output) of the lamp will begin to decrease.
Because of this, fluorescent lamps have an initial lumen rating and a mean lumen rating. The mean lumen output is measured at 40% of the lamp life.
NOTE: Decorative or colored bulbs do not have a lumen rating since they are not considered a primary source of lights, only decorative.
The shape of a bulb is followed by its maximum diameter, expressed in eighths of an inch. For example, a R40 has a maximum diameter of 40 eighths of an inch which equals 5".
The chart below will help you to quickly make these conversions.
Eighths of an inch - Inches
| 1 - 0.125 | 11 - 1.375 | 21 - 2.625 | 31 - 3.875 |
| 2 - 0.25 | 12 - 1.5 | 22 - 2.75 | 32 - 4 |
| 3 - 0.375 | 13 - 1.625 | 23 - 2.875 | 33 - 4.125 |
| 4 - 0.5 | 14 - 1.75 | 24 - 3 | 34 - 4.25 |
| 5 - 0.625 | 15 - 1.875 | 25 - 3.125 | 35 - 4.375 |
| 6 - 0.75 | 16 - 2 | 26 - 3.25 | 36 - 4.5 |
| 7 - 0.875 | 17 - 2.125 | 27 - 3.375 | 37 - 4.625 |
| 8 - 1 | 18 - 2.25 | 28 - 3.5 | 38 - 4.75 |
| 9 - 1.125 | 19 - 2.375 | 29 - 3.625 | 39 - 4.875 |
| 10 - 1.25 | 20 - 2.5 | 30 - 3.75 | 40 - 5 |
11. Where can I find information about lighting conferences?
For an up-to-date list of GE Lighting & Electrical Institute conferences, including schedule and registration information, visit the Conferences section of our web site.
12. What is a footcandle, and how can I calculate it for lighting a room?
A footcandle is unit of illuminance or light falling onto a surface. It stands for the light level on a surface one foot from a standard candle. One footcandle is equal to one lumen per square foot.
To calculate the footcandles of a lamp, divide the lamp's lumens square footage of the room. The lumen rating is usually listed on the lamp package. It's a lot easier (and probably more precise) to just take a reading with light meter.