1. Where can I find lighting
terms and technical information?
Our Glossary
& Know About
Light section can answer some of your questions about
technical lighting terms (like "What's an amp?" and
"How do fluorescent lamps produce light?")
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2. How can I get lighting
product catalogs?
Downloadable PDFs, including
the latest product catalogs with in-depth product specifications
are located in the Products menu of this web site.
+Download
Product Catalogs
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3. What are lamp BTUs?
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.
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4. How can I find the
surface temperature of a lamp?
FIREFLY 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
used, such as its baffling, reflection, insulation, and ventilation
properties.
For more information, contact
your fixture manufacturer directly. Fixture manufacturers are
able to specify the maximum wattage and bulb shape of the lamp
which can be safely utilized in your fixture.
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5. 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.
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6. What is efficacy?
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.
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7. 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.
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8. What is the mean lumen
output of a fluorescent lamp, and how is it different from the
initial lumens?
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.
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9. How is lamp diameter
measured? How can I determine the diameter of the lamp from the
lamp name or description?
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
2 - 0.25
3 - 0.375
4 - 0.5
5 - 0.625
6 - 0.75
7 - 0.875
8 - 1
9 - 1.125
10 - 1.25 |
11 - 1.375
12 - 1.5
13 - 1.625
14 - 1.75
15 - 1.875
16 - 2
17 - 2.125
18 - 2.25
19 - 2.375
20 - 2.5 |
21 - 2.625
22 - 2.75
23 - 2.875
24 - 3
25 - 3.125
26 - 3.25
27 - 3.375
28 - 3.5
29 - 3.625
30 - 3.75 |
31 - 3.875
32 - 4
33 - 4.125
34 - 4.25
35 - 4.375
36 - 4.5
37 - 4.625
38 - 4.75
39 - 4.875
40 - 5 |
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10. 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.
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